Remove pointsownedby from azimuth to save gas #50
Description
Spawning/transferring an azimuth point currently costs tens of USD. Some of that gas[1] goes to keeping the pointsownedby mapping up-to-date. If we imagine all 4 billion points being spawned, that's quite a lot of value. (even just moving all 65k stars onto Layer 2 will cost a good chunk of change.)
It seems that the only use for this mapping is the balanceOf function in the ecliptic's ERC721 interface. I doubt that's called by any contract, or ever really will be. It doesn't seem that useful. It's probably called lots by off-chain clients (token trackers and wallets). I propose that we either (a) abandon the ERC721 interface; or (b) return balance=0, and let those clients just be wrong; or (c) implement balanceOf by iterating through all 4 billion points and counting how many have owners that match the given address. This would be slow, but it's better for off-chain clients to be slow for a cosmetic function than for on-chain contracts to be charged gas for essential functions.
[1] I don't know what proportion, but someone could and should estimate it.