Contracts interface expansion

[jacogr]

0. Modify contracts/Registry to have lookupMeta (interface to contract get) method
1. Fixed contracts/GithubHint to retrieve instance properly & add getEntry to retrieve a specific entry

(Split from https://github.com/ethcore/parity/pull/4178)

[jacogr]

Implementation aligns with what we have in the others in ~/contracts now - previously it actually didn't work at all.

[ngotchac]

Wouldn't it make sense to now use this lookupMeta method in lookupAddress instead of having twice the same code?

[jacogr]

I had it that way around initially since it is 99.9% shared. Not sure why it was reverted, will take a re-look.

[jacogr]

I see why... one calls get the other getAddress on the underlying contract. (We don't have Uint in yet, haven't used it at this point in time)

So the options would be to pass the name, key as well as the relevant contract method to some helper to call the contract or to duplicate for code clarity.

I opted for the latter approach.

[ngotchac]

Ah yes good call. Well I guess that's fine, it small enough. Could have a

getLookupParams (_name, key) {
  const name = _name.toLowerCase();
  const sha3 = this._api.util.sha3.text(name);

  return [sha3, key];
}

method though