userportal, webadmin: fix popup dialog header text spacing

Changed popup dialog header text to be spaced with CSS only.

Popup dialog header text was shifting left over the icon. This
was a regression. Hopefully permanently fixed by restructuring
the layout of the dialog header bar. Now when an icon is present,
CSS takes care of moving the header text over.

Also cleaned up some CSS class names for the dialog header.

Change-Id: I28ffde8e344b1bedc10310f6eb814a37a7aecefe
Signed-off-by: Greg Sheremeta <gshereme@redhat.com>