Add user types to profiles

Very simple change @houndci @cgruppioni @georgetmayorga
```account_class.create(profile_id: id)``` passes the profile's ID to the account's profile_id column.  It's not the same as the ```account_id``` foreign key for the polymorphic type ```account``` in profile.

The profile ```belongs_to``` an account, and an account ``has_one``` profile.

Though, I think that makes the ```profile_id``` column in the account redundant and may be a huge cause of headache...