Handle additional key combinations

[aiongg]

Currently for many key combinations, we collect them but do not handle them. We need to decide which combinations we will handle and for what purposes, and otherwise allow them to be passed back to Windows. For example, Shift + Arrow keys normally allows the user to select text in the input field. We probably want to keep this behavior, so we should not collect Shift + Arrow.

These checks and pass/reject should happen somewhere in KeyEventSink.