Name wallet protocol subscription messages consistently

[Rigidity]

Makes the names of wallet protocol messages consistent with the rest of the code and the docs.

register_interest_in_coin => register_for_coin_updates
register_interest_in_puzzle_hash => register_for_ph_updates
respond_to_coin_update => respond_to_coin_updates
respond_to_ph_update => respond_to_ph_updates

[arvidn]

it's a little bit scary given that we use runtime reflection to call functions with the same names as those classes. who knows what other names may be connected to these at run-time.

[richardkiss]

Sorry for the delay. Github sure makes it hard to resolve conversations that are outdated.