Shifted all the execution code into the gui_bieri.execution package.
This redesign is discussed at https://mail.gna.org/public/relax-devel/2010-01/msg00054.html
(Message-id: <7f080ed11001210133h32ab3304l64a0474ab7ac1a1c@...>).
The execution code is the layer between the GUI and the relax internal API. This currently
implements the automatic analysis types. This package might be shifted in the future to be used by
other UI designs.