Adding a flag to the Mouse to allow us to detect and handle tap-to-click

Adding a flag to the Mouse to allow us to detect and handle tap-to-click on trackpads, which frequently are missed in normal polling because the drivers (at least on Apple hardware) send both a down and up event when the finger is lifted, which usually means both events are processed on a single frame.

Also did a tiny optimization to the keyboard key removal by checking the result of Remove rather than calling Contains to avoid walking the list twice.

Tested this with my MacBook Pro in Windows (using Bootcamp) and in OS X and works fine with my hardware on those platforms.