Create a User Accounts plug [$340]

A user accounts plug should be created that can:

- Create accounts
- Remove accounts
- Edit a user's first and last name
- Set a user's avatar
- Add a user to Dexter automagically
- Open a user's contact data in Dexter
- Set a user's account type
- Change a user's password
- Enable/disable the guest account

I've attached a mockup of what this might look like.