add_garageadmin_account

### Changelog
* Created role to setup garageadmin account dealing with issue #3
* creates a new user account for garageadmin
* sets the password
* creates necessary directories
* assigns Admin privileges to account
* referenced in [this trello card](https://trello.com/c/QUyJSFTg/441-automate-creation-of-garageadmin-account-in-osx-bootstrap)
[security] password can not be stored in plaintext.

It either needs to be hashed or input by the user at runtime.