relax SVN archive

Better handling of the return to the initial GUI screen.

This was broken on MS Windows.

add_start_screen() now re-performs a main window layout.

This allows for a proper layout once all analysis tabs have been deleted.

If all analyses are deleted, then the initial GUI state is set and the start screen remade.

The initial sizer with the relax icon is now properly deleted.

Fix for the R1 and R2 analysis tab initialisation.

This bug was introduced in the last commit.

The relax data store GUI analysis elements are now only initialised by the analysis classes if asked.

By passing in an index for a currently existing analysis data structure, a new structure will now
not be initialised by the analysis classes.

Fix for the from_xml() method based on the change to add() in the GUI analyses data object.

Fix for the GUI Analysis.add() method for returning the index of the container.

The add() method of the GUI analysis part of the relax data store now returns the index.

This is rather than the data container itself.

The state_save() method no longer needs to sync the individual analyses.