Implemented ECDSA recover function. (#914)

* Implemented ecdsa recovery function.
Added method `to_eth_address` and `to_account_id`.
Added tests.

* Cargo fmt

* Added `ECDSA` and `Ethereum` to dictionary

* Fixed comments according a new spellcheck

* Fixes according comments in review.

* Fixed build issue for wasm

* Use struct instead of alias for `EthereumAddress`.

* cargo fmt --all

* Simplified `ecdsa_recover`.
USed symbolic links instead files.

* Added documentation for `to_eth_address` and `to_account_id` methods.

* Renamed `to_account_id` into `to_default_account_id`

* Cargo fmt

* Removed DeRef trait. Now field of `EthereumAddress` and `ECDSAPublicKey` is private.

* Fixed doc test for ecdsa_recover in EnvAccess