TriggerMenu: Further python3 fixes
- Fix relative imports.
- iteritems
- can't use -1 for level in import
- use zip instead of map with a null function
- print function.
- generators -> list
- builtin -> builtins
- comparison/sort incompatibilities
- integer/float division
- metaclass fix
- exec statement
(Still have to fix uses of exec to set local variables. Will be addressed in a subsequent merge, to keep this one from getting too big.)