Decouple accounts-password from transports

[cunneen]

accounts-password has a tight coupling with email. This is restrictive. While accounts-password has a lot of nifty features (password verification, change, reset etc), email is not the only possible transport. For example, you might want to use SMS, or a DM in Slack or Gitter.

I'm not proposing the implementation of these other transports, just the decoupling of accounts-password's core functionality from the particular transport. The new accounts-password-transport-email would then become the reference implementation.

[mariusrak]

I agree, current implementation of accounts-password is too restrictive. It should just provide low-level functions, like providing enrollment/reset token and maybe for specifying callbacks on events.