Replace Token Auth with Basic Auth + Keychain

[catsby]

The app currently uses a Users's token for authentication. My original intention was to avoid asking for the users password if I didn't have to.

With OAuth being added, token based auth all but official depreciated in v3, no foreseeable xAuth/desktop workflow being added, we need to switch to using basic auth.

Storing the users password in the keychain is really already supported, we store the token there right now. Need to switch to using password, and gracefully transition others over from token based.