Exports should group by name instead of all into one

[hexonaut]

Fixes an issue where exporting to multiple jsons at once would not separate by name.

Ex)

ScriptTools.exportContract("A", "someContractA", address(123));
ScriptTools.exportContract("B", "someContractB", address(456));

before this would output both contracts someContractA and someContractB to the B.json. With this change both A.json and B.json will have only their 1 respective contract.

[DaiFoundation-DevOps]

All committers have signed the CLA.

[amusingaxl]

Can you please explain a little bit further what issue you are trying to fix here?

[hexonaut]

Updated OP

[amusingaxl]

This actually makes sense. LGTM.