Restrict users to only see peers in their groups

Have a global setting called “Restrict users to only see peers in their Groups” which made it so that Group Admins / Users could only see other users in the groups.

For example

Group A: User 1, User2, User3
Group B: User 4, User3
Group C: User1, User5

User 1 can see: User2, User3, User5
User 2 can see: User1, User3
User 3 can see: User1, User2, User4
User 4 can see: User 3
User 4 can see: User 1

Prior discussion: https://github.com/xibosignage/xibo/issues/113

Workarounds:
Changes to lib/app/permissionmanager.class.php after Line #71

if ($this->user->usertypeid == 3) {
    $this->modifyPermissions = false;
}

also need to add the same at the end of the FullAccess() function in that same file.