A working keypress implementation

Hi everyone,

this should be a working keypress implementation. As you can see by the number of commits, I extended the original work quite a bit... there are just so many edge cases.

like:

* shift is not used as a modifier key normally, only when you use special keys
* just hitting modifier keys yields nothing
* when control is pressed SWT returns different strings
* ...

Everything is nicely specced/mocked with what I observed SWT does (I dare them to change it!!!) and I hope that the code is understandable.

Feel free to try out the sample script. **Be aware however** that it just instantly prints the pressed keys **to the console** and not to the **GUI** as there is clearly a redrawing missing somewhere... but I'll open a separate issue for that. 

Feedback very much welcome as always :-)
Tobi