enhancements to waltz.Account

- Added salt kwarg to Accoung.registration for reproducable hashes
- Added documentation
Fixed db.get(safe=True), added db.getall()

- Added User.getall()
- User(uid) results in a User obj which triggers User.get() and populates self as Storage obj
- fixed User.registration to send kwargs to Account.registration rather than user.update in User.registration
- Added docs
more comprehensive test cases for Account + User
security: removed uhash and salt from User obj __repr__