Add L2 reverse registrar contract

[jefflau]

• Resolver profiles for setName and setText
• Signature record setting for setName
• Signature record setting for setName for an Ownable contract
• Signature record setting for setText
• Signature record setting for setText for an Ownable contract
• Signature record setting for clearRecords

[makoto]

What is the rational of the reverse registrar having setText which wasn't the case for L1 reverse registrar? Also, if there is a valid reason for it, what's the reason of reverse registrar not having setAddr either?

[makoto]

More of a general observation but do they have any L2 specific traits about these contracts? The majority of the work is to allow registration by signature which is useful on L1 as well. Can we make this as a default name registrar on L1 as well?

[makoto]

You probably need to add function supportsInterface

[jefflau]

You probably need to add function supportsInterface

I think there is already a function there?