relax SVN archive

The Execute.run_analysis() base class method has been created.

This raises a RelaxImplementError if called!

The run() thread (and pseudo-thread) method has been shifted to the Execute class.

The derived classes must now provide the run_analysis() method.

A dummy join() method has been created to make the non-threaded execution behave like a thread.

Simplification of the threading setup in the Rx analyses.

Modified the threading execution of the GUI analyses.

The class gui.analyses.execute.Execute has been created to be a base class for all the analysis
threads. The specific analyses then only need to derive from this by providing the run() method.
All of the threaded vs. non-threaded, exception handling, and other threaded properties will then
be handed by this class.

Fix for the sequence data in assemble_data().

Removed an unused import.

Fixed the import of the threading module.

Removed an unused import.

The higher level threading.Thread class is being used rather than thread.start_new_thread().

This matches the NOE analysis changes of r13255.