webadmin: Events tab - Details dialog

Events tab:
* Created a new dialog for showing event's details (ID, Time, Message).
  Event message is displayed in a text-area for easy copy-paste.
* Added context menu 'Details' button (invoked on double-click)

Change-Id: If9bccd2e8a692dd7f9745ed240de3ebd1b7ff376
Signed-off-by: Daniel Erez <derez@redhat.com>