[MonoDevelop] Edit References dialog

[John Luke]

Hello all,
	The current Edit References dialog is a bit awkward.  I was thinking it
might be a great little task for someone to go through it and clean it
up or redesign it a bit.

Some ideas:
 - remove the list of referenced assemblies on the bottom
 - improved and consistent naming (.NET Assembly, Global Assembly Cache)
 - maybe embed a filechooser widget instead of opening another dialog
   to select a .NET assembly
 - maybe keep a list of common and or recent assemblies
 - the conceptual equivalent of -pkg:gnome-sharp (which in turn includes
its dependencies)
 - general UI clean up
 - whatever else others find lacking