Mouse, touch, and pointer

As it stands as of v0.5

I handle mouse and touch separately, since I'm allowing multiple touches (but not... multiple mice?). This results in a fair bit of redundancy since adding to the stroke tracker is doubled a la ___MouseEntry vs ___TouchEntry, but that will likely be corrected by a refactor before v1 release.

Since both mouse and touch have pageX and pageY they work basically the same otherwise, though mouse inputs are not single point, resulting in bugs like #3. Pointer probably needs to be implemented to handle stylus inputs, since they otherwise lock things up and defeat the fun parallelism of multi-touch+stylus+mouse I aim for.