User groups management

As an Owner I'd like to be able to add/edit/delete User Groups.

1. Group name on "User Groups" page is link to page for selected group managing.
2. There is button "Create new group" on "User Groups" page.
3. Group page contains following items:
   • group name and description;
   • blue "Edit" button;
   • red "Delete" button (should be inactive for predefined groups: Administrators, Moderators, Registered Users, Banned Users).
   • user managing block:
     • search field and table for users who are in current group;
     • buttons to move user to/out of group;
     • search field and table for users who are not in current group;
4. After pressing "Edit" button popup (same as for branch editing in administration mode) apperas with following items:
   • input for group name (filled with current group name);
     • 1..255 symbols;
     • can't be empty;
     • can't contain only space;
     • spaces at the begin and at the end are trimmed.
   • input for group description (filled with current group description);
     • 0..255 symbols;
     • can be empty;
     • can't contain only space;
     • spaces at the begin and at the end are trimmed.
   • "Save" and "Cancel" buttons.
5. User tables have pagination, one page has 50 entries
6. User tables have three columns: checkbox for user selecting, "Username" and "Email".
7. Table "Users in group" contains all users in current group.
8. Table "All users" contains all registered users exсept users from current group.
9. Buttons for users moving:
   • move selected user(-s) to group;
   • remove selected user(-s) from group;
   • move all users to group;
   • remove all users from group;
10. Users moving occurs without page refresh. Only user tables are refreshed.