and change the dialog from a editor of the display's devices to an
editor of all devices of all displays known to GIMP, regardless
whether currently plugged or just remembered in devicerc. will need to
distinguish them in the next step...
Added two new widgets, GimpDeviceInfoEditor, which is an editor/view
widget for GimpDeviceInfo, and GimpDeviceEditor, which is an editor
widget for all devices. Both are pretty much ugly right now and look a
lot like the old GtkInputDialog, but are at least internally cleaned
up and easily changable code and ui wise. Consider this a completely
intermediate state.
Also cleaned up GimpDeviceInfo so it's possible to have a proper
view on it, and did the needed changes to the preferences dialog
to use the new stuff.
