relax SVN archive

This follows from http://thread.gmane.org/gmane.science.nmr.relax.devel/4530, the thread about
supporting multiple data types such as SQ+MQ data simultaneously.

The popup menu must be generated on the fly, as the CPMG frequency and spin-lock field strength menu
entries should only be shown for the appropriate experiment type. Therefore the new
generate_popup_menu() method has been added to the gui.components.base_list GUI element. The flags
sent into the spectrum list GUI element have also been completely changed to now indicate the
analysis type directly.