userportal, webadmin: Dialog box header drag

- The drag box on dialogs was only 20 px high, while
  the header was 36 px high. This caused it to not be
  clear where you could and could drag the window. This
  patch makes the entire header dragable.
- Replaced tabs with spaces in DialogBox.css.

Change-Id: I712203d343102c1a61f5256eb0eefbe7162a1d78
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1139634
Signed-off-by: Alexander Wels <awels@redhat.com>