[GREENFOOT-509] Allow modifier+extension to take effect from slots in the frame
As previously discussed, as well as allowing "f" for final before/after a var frame, allow modifier-f (and show in cheat sheet) from inside the var frame slots.
(Note: modifier was going to be Alt, but on Windows, that triggers the menu mnemonics. Ctrl-Alt seems to be used for entering non-ASCII chars so don't want to interfere with that. Went with Ctrl-Shift as a reasonable alternative.)
- Issue type: Task
- Priority: Medium
- Fix versions: 3.0.3