Support other modifier keys

[shtanton]

I was messing with the code for doClick and doDrag and noticed a todo for the other modifier keys as only shift is handled at the moment.

I could write a type for them with 3 boolean fields for ctrl, alt and shift and a method to convert to a number for core maybe? Or just something with numbers and an enum.

It wouldn't actually do anything until we bound something to the combinations but if it sounds like a good idea I'll send a pull request.

Edit:
Is the repo still alive?