Updates to avoid PyGIDeprecationWarning
Support the use of the system store with recipes

This is especially important now that we treat all downloads as recipes!
Allow relative files in <archive> and <file> for local feeds

This makes it easy to test feeds before passing them to 0repo.
Allow selecting local archives even in offline mode
Keep gobject and glib separate

Sometimes we need GLib, sometimes we need GObject.
Better error when the <rename> source does not exist
Cope with more PyGObject API changes

Based on patch in http://twistedmatrix.com/trac/ticket/6369