* Update Send transaction UI so "amount" field can be 0, since some users may want to just send some data (i.e. https://github.com/chainx-org/ChainX/issues/66)
* Set the default amount value to be 0 and not required
* Update Send transaction UI to support "data" field in hex (with 0x prefix)
* Use a hard-coded Gas Limit of 200,000 when user provides hex "data" value
* Remove logic that doesn't make sense (i.e. `else if (amountBn.isZero()) {`)
* Update validation messages
* Add support for Blockscout link when user using Goerli testnet
* Update internationalisation
* Use custom `isHexString` function instead of the ethereumjs-util's version. The ethereumjs-util's version is used by MyCrypto and doesn't work properly.
* Tested on Goerli testnet by creating two accounts, requesting Goerli tokens, running with `--chain goerli` appended to the end (i.e. `"start": "cross-env ELECTRON_START_URL=http://localhost:3000 electron-webpack dev --chain goerli",` in fether/packages/fether-electron/package.json), and sending a transaction with the high gas price, the hex data. For example, for ChainX convert your ChainX Address (UTF8 chars) into Hex code (i.e. copy/paste it at https://www.browserling.com/tools/utf8-to-hex, for example "helloworld" becomes => `\x68\x65\x6c\x6c\x6f\x20\x77\x6f\x72\x6c\x64`, and remove the `\x`, => `68656c6c6f20776f726c64` => then prepend 0x => `0x68656c6c6f20776f726c64` and add that to the "data" field), then send the transaction, and
when the transaction is successful go to the Blockscout link and you'll see under "Raw Input" ("Input Data" on Etherscan) that you can switch between viewing it in UTF8 or Hex, i.e. https://blockscout.com/eth/goerli/tx/0x7eaec61ce7753fd4c80aec4509c49942b53986585e4864e18134806bffb25f10/internal_transactions)
* TODO - update Parity Signer to show "data" field value if it doesn't already

feat: Relates to #360. Only allow import from Parity Signer chain account matching current chain. ETC support (#483)

* feat: Relates to #360. Only allow import from Parity Signer chain account matching current chain. ETC support

* review-fix: Refer to non-Parity chain names in the UI. Add console.error

* review-fix: Do not need to chcek health status before calling chainId RPC of light.js on pages accessed through navigation

* review-fix: Rename function name that matches current chain id with imported chain id of address

* review-fix: Remove unnecessary function

* review-fix: Rename function to accountAlreadyExists

* review-fix: Remove FIXME. See https://github.com/paritytech/fether/pull/483#discussion_r270834847

* review-fix: Refactor to use util functions isEtcChainId, chainIdToString, isNotErc20TokenAddress

* fix: Fix typo in comment

* review-fix: Change wording of parity phrase comment

* review-fix: Do not clear isImport as not account related

* fix: Clear error so error when recover from seed phrase not still shown if then click to recover from QR code

* fix: Rename so signerChainId correctly destructured and not undefined

* review-fix: Remove async/await from clear

* fix: Avoid mapping signer chain id to chain name since too much maintenance with Parity Ethereum

* review-fix: Remove await from createAccountStore

* tests: Add colour to fether-react tests

* refactor: No need to parseInt on the signerChainId

* refactor: Use isNotErc20TokenAddress

* refactor: Use isNotErc20TokenAddress again

* refactor: Add isErc20TokenAddress util so more readable

* fix: Replace valueOf with .eq. Fix so obtain BN from props

* refactor: Combine into single if statement when checking if valid Eth/Etc address

* refactor: Update utils without unnecessary return block

* chore: Update to latest React 16.8.3 to requirements of react-i18next

* feat: Scaffold basic translation with English and German

* feat: Relates to #402. German translation fully working

* fix: Switch back to English by default

* fix: Allow user to switch between languages in preferences of context menu

* feat: Translate the context menus

* refactor: Remove German language. Add as separate PR

* refactor: Remove blank line

* docs: Update Readme with Internationalisation Add New language instructions

* docs: Update Readme with Known Issues and Usage instructions

* review-fix: Disabled tooltip Please fill out this field. Add High and Low tx speed

* review-fix: Update license headers to be 2019 instead of 2018

* review-fix: Change ns1 to fether-electron and fether-react. Use pino.debug

* fix: Add missing i18n conversion for macOS Edit menu

* review-fix: Remove unused i18next browser languagedetector dependency

* merge latest from master and fix conflicts

* merge latest master and fix conflicts. TODO do not expose remote

* fix: Do not expose remote. Only expose add and remove listener, and reload via bridge

* feat: Convert new release available text to i18n

* Move toggle details buttons and associated methods and showDetails state into nav of TxForm component

* Pass showDetails down as props to TxDetails

* Remove previous attempt to display TxDetails like a popup above other fields
(i.e. remove form-details-wrapper and -details-value styles)

* Move "Details" / "Hide" buttons into the form-nav footer section

* TxDetails now appears above the footer area above other input fields without causing the screen height to increase

* Background of the TxDetails darkened so it stands out from surroudings

* Change "Details" arrow to point upwards since TxDetails now shown above

* Change "Hide" arrow to point downward since TxDetails now shown above

* Rename classnames to `_` or `-` more consistently

* Note: To quickly display the 'Details' button so you can click it change TxForm.js as follows:

```
{/* {valid && this.estimatedTxFee(values) ? ( */}
  <TxDetails
    // estimatedTxFee={this.estimatedTxFee(values)}
    estimatedTxFee={new BigNumber('8100000')}
    token={token}
    // values={values}
    values={ { amount: new BigNumber('0.1'), gasPrice: new BigNumber('21000') } }
  />
{/* ) : null} */}

Note: It is necessary to have no indentation otherwise spaces are interpreted.

See discussion of options: https://github.com/paritytech/fether/pull/307#discussion_r244695598

* Remove `isEstimatedTxFee` since can just use `estimatedTxFee` to achieve same functionality

* Rename `newEstimatedTxFee` to `newGasEstimate` since it returns a value that's used for the `values.gas` prop

* Update `estimatedTxFee` to return `null` if the amount, gas, gasPrice values provided aren't valid, instead of returning the calculated estimated tx fee

* Wrap call to `estimateGas` in a try/catch block that throws error "Unable to estimate gas" when error thrown when calling `estimateGas` in TxForm.js

* Move check `if (!ethBalance) {` earlier in function

* Create TxDetails component and move relevant instance methods from TxForm into TxDetails

* Fix linting warning `Using target="_blank" without rel="noopener noreferrer" is a security risk: see https://mathiasbynens.github.io/rel-noopener`