Chainspec validation

[debris]

changes:

• new executable which verifies chainspec json files
• scrips/validate_chainspec.sh which validates our chainspecs
• fixed invalid chainspecs

validate_chainspec.sh output looks like this:

ethcore/res/authority_round.json is valid
ethcore/res/basic_authority.json is valid
ethcore/res/constructor.json missing field `gasLimitBoundDivisor` at line 11 column 2
ethcore/res/instant_seal.json is valid
ethcore/res/null.json is valid
ethcore/res/null_morden.json is valid
ethcore/res/tendermint.json is valid
ethcore/res/validator_contract.json is valid
ethcore/res/validator_multi.json is valid
ethcore/res/validator_safe_contract.json unexpected field `engine.?.params.gasLimitBoundDivisor`
ethcore/res/validator_safe_contract.json unexpected field `engine.?.params.gasLimitBoundDivisor2`
ethcore/res/ethereum/classic.json is valid
ethcore/res/ethereum/eip150_test.json is valid
ethcore/res/ethereum/eip161_test.json is valid
ethcore/res/ethereum/expanse.json is valid
ethcore/res/ethereum/foundation.json is valid
ethcore/res/ethereum/frontier_like_test.json is valid
ethcore/res/ethereum/frontier_test.json is valid
ethcore/res/ethereum/homestead_test.json is valid
ethcore/res/ethereum/kovan.json is valid
ethcore/res/ethereum/metropolis_test.json is valid
ethcore/res/ethereum/morden.json is valid
ethcore/res/ethereum/olympic.json is valid
ethcore/res/ethereum/ropsten.json is valid
ethcore/res/ethereum/transition_test.json is valid

[debris]

According to gitlab, rust job succeeded. It was just not reported here

[eira-fransham]

Unnecessary ls, just do for spec in path/to/dir/*; do. Iterating over ls output is unstable anyway. Also, backticks are deprecated and also smell and are bad.

Hey, instead of me telling you this stuff, go install Shellcheck since I think both of those notes are implemented as lints.

[debris]

thanks! I will check it out :D

[eira-fransham]

I think that Foo: AsRef<Bar> as a type parameter is unnecessary because of Rust's automatic coercion (for example, foo(&bar) will succeed if foo takes a &T and bar implements AsRef<T>). I think I've made this same mistake in my latest PR with AsRef<Path>. So this could just take &str with the same API.

[eira-fransham]

I've got some nits but I'd be happy with this being merged. You can fix them up if you like, but it's not a problem.

[arkpar]

But we already have a unit test that does that. See #6028

[debris]

So there are few reasons to actually have chainspec executable:

1. currently there is no way to validate a json file which is not a part of parity repo. I needed this
2. unused fields are not checked
3. currently not every json file in ethcore/res/ and ethcore/res/ethereum/ is checked and we have to remember to update the test if we add new spec

2 && 3 can be addressed with improved unit tests, but 1 not

[debris]

@arkpar I removed existing tests

[rphmeier]

Agreed with @debris on this -- the broken chainspecs in the repo were all not covered by the tests when I made my PR.