Make sure that --dev purge-chain is rejected

```
[0] [11:24:02] ~/r/polkadot master > ./target/debug/polkadot purge-chain --dev -y
"/home/cecile/.local/share/polkadot/chains/dev/db" did not exist.
[0] [11:25:36] ~/r/polkadot cecton-fix-invalid-argument-order > ./target/debug/polkadot --dev purge-chain -y
error: Found argument 'purge-chain' which wasn't expected, or isn't valid in this context

USAGE:
    polkadot --dev

For more information try --help
```

* Be specific about the `BitVec` generic arguments

Currently we use the default generic arguments for `BitVec`. This means
we use `BigEndian` and `u8`. These default values are not stable, with
`0.17` of the `BitVec` crate this changes. To make sure we don't break
anything in the future, make sure we explictly set the generics.

* Update `spec_version`

* Initial commit

Forked at: 6a2092d6
Parent branch: origin/master

* Test running node and interrupts

* WIP

Forked at: 1942ae27ae23809a40f955545dfbf0467faa7750
Parent branch: origin/cumulus-branch

* Update Cargo.lock

* WIP

Forked at: 1942ae27ae23809a40f955545dfbf0467faa7750
Parent branch: origin/cumulus-branch

* WIP

Forked at: 1942ae27ae23809a40f955545dfbf0467faa7750
Parent branch: origin/cumulus-branch

* WIP

Forked at: 1942ae27ae23809a40f955545dfbf0467faa7750
Parent branch: origin/cumulus-branch

* enable migrations in polkadot and kusama runtimes

* bump runtime version

* runtime: candidate receipt must pass parent head

* construct parachain candidates using correct parent_head

* validate that the parent header is correct in candidate receipt

* fix test fallout

* bump runtime versions

* Amalgamate pieces of balance module

* Fixes for vesting split

* Refactoring for vesting/balances split

* Build fixes

* Remove on_free_balance_zero and some docs.

* Indentation.

* Revert branch

* Fix.

* Update substrate: fixes after CLI refactoring

* Reverting removal of exit

* Removed too much again

* Update Cargo.lock

* Cargo.lock

* Update Substrate, ready for #4820

* Fixes

* Update to latest substrate master

* Fix network tests

* Update lock

* Fix tests

* Update futures to get bug fixes

* Fix tests for new balances/vesting logic

* Cargo fix

* Another fix

Co-authored-by: Cecile Tonglet <[email protected]>
Co-authored-by: Robert Habermeier <[email protected]>
Co-authored-by: Bastian Köcher <[email protected]>

* Fix browser.rs

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <[email protected]>

* Bump runtime version

* Bump runtime version

* Update to latest Substrate master

* upgrade decl_storage declaration

* Companion PR to Substrate#4752

* Substrate update: Identity should bound additional fields (#4770)

Substrate commit: 2c9ce7296b19934b1ffd50150be2fdb2ddf81a4e

* WIP

* WIP

* Updated substrate and fixes

* Fix compilation and switch to latest wasm-builder-runner

* Fixed missing doc

* Update collator/src/lib.rs

Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: thiolliere <[email protected]>
Co-authored-by: Pierre Krieger <[email protected]>
Co-authored-by: Cecile Tonglet <[email protected]>

* Update to latest Substrate master

* upgrade decl_storage declaration

* Companion PR to Substrate#4752

Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: thiolliere <[email protected]>
Co-authored-by: Pierre Krieger <[email protected]>