Ink Player Window should autocomplete function and variable names

[tomkail]

This'd be a real boon! I guess there are algorithms for this floating around.

[tomkail]

I had a serious stab at this using some code I found online, but unfortunately due to the way IMGUI works you can't easily have buttons that overlap each other, and so this becomes really difficult to do properly.

[tomkail]

Note: should also include list element parameter values