LP#1468422 Password storage/migration SQL getting started

LP#1468422 Password storage/migration SQL getting started

* Backwards compatible salted password storage using pgcrypt
* Adds actor.passwd and actor.passwd_type tables
* Includes pgtap tests
* Includes installation of pgcrypto

Current flow:

1. Application requests a salt to use as the CHAP-style seed
2. If new-style password exists, salt is returned.
3. Else, old password is migrated and the new salt is returned.
4. App finalizes login by checking verify_passwd.

== continued...

Store the iter_count and start using the crypt_algo column.

Make it possible to change the salt, and potentially strengthen
the salt, when changing passwords.

Make is possible to start salt-less passwords, for pw's that are managed
outside of the DB.

Signed-off-by: Bill Erickson <berickxx@gmail.com>