CAT.save:
* Move to separate file
* Allow direct specification of output name
* If no output given, use the variable name used on command line
* Allow return of output filename if requested
CAT.load:
* Move to separate file
* Allow loading directly from another workspace object
CATTube.save:
* Move to separate file
* Rename from saveCAT to save
* Use CAT.save
* Use GUI to give file name
CATTube.load:
* Move to separate file
* Fix error occurring if cancel button pressed