relax SVN archive

Created an observer object for changes to the GUI analysis tabs.

The execution of the callback functions in the observer objects is now ordered.

This is based on the registration order.

Fix for the relaxation data list GUI element - the frequency value was being set to the wrong col.

Fixes for the grid GUI elements - the first row which is not deleted is now being cleared of all text.

The data pipe editor can now be opened with Ctrl+D.

Fix for the popup menu in the data pipe editor - the row and column were swapped.

Fixed an accidentally deleted import of the status object.

Changed the pipe_switch observer object to pipe_alteration and all pipe changes are now signalled.

Implemented the data pipe editor window.

This will be used to manipulate data pipes including how they interact with the GUI.

Converted the menu build_menu_item() method into a function of gui.components.menu.

This allows it to be used more easily by other parts of the GUI.