Signin error notifications kept from stacking

closes #3375
- Prior to showing error notifications, the signin route now calls
  closePassive().
Signin: Proper notification if user not found

closes #3374
- If user object is returned but undefined, we'll display a
human-readable
error notification (user model)
- If user object is returned, but the user is inactive or invited (but
not
activated), we'll display a human-readable error notification
Hides <Users button for authors

closes #3295
- The <Users button visibility is now restricted by user role
Fixing resend user invitation

closes #3396
- passing role when resending a users invitation
Removing "full name" auto-popualtion during signup

closes #3392
- removing data-binding attribute for "name" input box on signup screen
- removing data-binding attribute for "password" input box on signup screen
- making "email" the first input box and "name" the 2nd
- removing "autofocus" attribute for "email" input box on signup screen
Merge pull request #3385 from felixrieseberg/iss3375

Signin error notifications kept from stacking
Merge pull request #3386 from felixrieseberg/iss3374

Signin: Proper notification if user not found
Merge pull request #3394 from IanMitchell/settings-user-button

Hides <Users button for authors
Merge pull request #3398 from morficus/issue-3396

Fixing resend user invitation
Merge pull request #3397 from morficus/issue-3392

Removing "full name" auto-popualtion during signup
updated Ember Simple Auth to latest version
Merge pull request #3406 from simplabs/update-ember-simple-auth

Updated Ember Simple Auth to latest version