Add create_recovery_token method

[skeet70]

Add a convenience function that performs most of the worked laid out in the "Password Recovery Tokens" section of the data control platform guide. This function should take a password, generate a key, encrypt it, and return the key as a recovery token for display to an end user and the encrypted password (with iv on the front) for storage by the caller.

[skeet70]

See this for some more discussion if possible.

[ernieturner]

Needs more design of the best way to implement this, maybe we encrypt their private keys instead of encrypting their password.