User creation & signin additions + cleanup

Multiple changes.

* eileenmcnaughton/civicrm_entity#5 - Extend support for creating users
* eileenmcnaughton/civicrm_entity#6 - Pass user creation error back to Drupal messages
* eileenmcnaughton/civicrm_entity#7 - Instant signin
* Some Drupal style cleanup

Can I suggest you create a new main branch 7.x-1.x to follow Drupal.org style here, and leave master at this point.