Adding 'success' messages for admin/users/edit.php (Bug #1314416)

Now should get succes messages for:
- saving Site account settings
- adding user to institution
- updating user institution settings
- removing user from institution

Change-Id: Ifc7de7950442e0e0be29a03c7bf2ba570e3e2d58
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>
Merge "Adding 'success' messages for admin/users/edit.php (Bug #1314416)"