Two user-interface issues with the GUI boot loader configuration.

* new dialog boxes (such as gotten by clicking on Add or Edit in the "Boot
Loader Configuration" section) have absolutely no border, making it impossible
to recognize them visually as pop-up dialog boxes.  That might be a general GTK2
issue for all I know....

* when adding an additional OS to boot, the dialog box asks for a label and a
device.  Although it's not clear from the UI, the device name expected is the
instance (eg, hda1), not the actual device path (eg, /dev/hda1).  I didn't
realize this, and wound up entering /dev/hda1 and so forth in the box, which
results in configs which reference /dev//dev/hda1.  I like the idea of the
interface automatically inserting /dev/, but I think it should make it clear
that it is doing so.  This could be done by using /dev/ as a label before the
dialog entry, something like:

Device:    /dev/[ THIS AREA BETWEEN BRACKETS IS THE DIALOG BOX]

which should help avoid confusion