Feat/bitcoin routing

Hooks up bitcoin wallet generator to backend

Walkthrough of transaction creation (will have to change name later):

- post to create with username and other username
- create new wallet + private key
- split private key in half
- find username
  - create new transaction for this user, with address and 1 half of key
  - save to db
- find other username
  - create new transaction for other user with address and other half of key
  - save to db