Keyboard callbacks passed to tgModel

[apsabelhaus]

NTRT currently lacks a way to pass keyboard callbacks to our own custom applications (specifically, our tgModels), at least in the master branch.

I've implemented this functionality in the laika branch, specifically that callbacks are passed through tgSimViewGraphics to tgSimulation then down to models.

I'm opening this issue now for others who may be interested in similar functionality. I don't have time to merge it back into master (the laika branch has diverged significantly from master by now), but if someone wants to do the merge, it would be appreciated. The required changes to tgSimulation, tgSimViewGraphics, and tgModel are in commit 79a843d in the laika branch.

Be careful when merging - only take the changes from those classes specifically. You'll break other people's code if you try to merge more of the laika branch back into master.