Add/Modify group translation
Add/Modify user translation
Modify user test data
Rework authentication ref #123
Modify Authentication for a more secure access

E-mail and username are now correctly stored in database.
ref #123
Change login-field to email-field and add translations

ref #123
Changed authentication process for admin, ref #123

 - moved unique constraint of Users identity_url to email
 - admin has nil identity_url
Removed unused method in seesion controller, ref #123
Fixed specs, ref #123
Added tests for authentication, ref #123
Fix creation of new user used by devise

ref #123