Fixed issue #634: Fixed adding and changing user roles for admin
Fixed issue #634: Added password validation

Now admin cannot create or modify user without
a password or with an unacceptably short password.
Fixed issue: More convenient form when an error occurs
New feature: Added initial Private Message helper with common constants
Fixed issue: Cleanup Message Model, moved common constants into PM Helper
Fixed issue: Cleanup Message Controller, moved common constants into PM Helper
Updated feature: Disabled tabs on compose and edit actions
Merge pull request #662 from sergeyklay/feature-bootstrap-3

User fixes and additions