webadmin: Element IDs in Assign Tags and Role dialogs

1. Assign Tags dialog (Users main tab) now supports
   element IDs for Tree nodes

2. Role dialog (Configure dialog | Roles tab) now supports
   element IDs for Tree nodes and some other UI elements:
   - Name and Description text box
   - User and Admin radio button
   - Expand and Collapse button

Change-Id: Ic37627d382d529fe7f8c11a55e6799a6d8617a6a
Signed-off-by: Vojtech Szocs <vszocs@redhat.com>