Remove unused Shoes::Swt::KeyEvent class
Filtering for keypresses to forward

Certain SWT controls--buttons, text, combos--have handling for some keypresses
on their own already, and in Shoes 3 wouldn't send those keys along to key
press handlers.

Since the SWT display filters we're using see all the events, to maintain
consistency with the old behavior, we try to manually filter out the events
that shouldn't get through.