* Migrate sellBet to v2
* Kill sellBet warmup requests
* Point client at new v2 sellbet function
* Clean up `getSellBetInfo`
* Fix up functions index.ts
* Rename `lib/firebase/api-call` -> `lib/firebase/fn-call`
This relieves ambiguity now that we will be using our actual
public API in the client.
* Rewrite client API calls to createContract, placeBet
* Tiny fixup for client market creation code