webadmin: added DecoratedPopupPanel tooltips to StyledImageResourceCell

Changed StyledImageResourceCell to use a DecoratedPopupPanel for its tooptip
instead of plain HTML titles. This makes the tooltip in comment columns (and
other places) match the tooltip styles elsewhere in the application.

Change-Id: I843f7f3baec6abe1695116ae2dc0580d102887b7
Bug-Url: https://bugzilla.redhat.com/990429
Signed-off-by: Greg Sheremeta <gshereme@redhat.com>