Issue #99 : withTouch() touchstart event was relying on direct access to...

Issue #99 : the withTouch() touchstart event handler was relying on direct access to the Processing.eventHandlers array to remove any existing mouse event handlers.

Instead of exposing Processing.eventHandlers array directly, this change exposes a method called detachEventHandlersByTypeMatch() which takes a regex of event types, iterates through the list of existing event handlers, and detaches the handlers that match.

The withTouch() touchstart handler then calls detachEventHandlersByTypeMatch() with a regex that matches the desired mouse events.
I included `touchstart` in the list, because it was in the original code.  Maybe it's in there to ensure that no one else added event handlers that might interfere with this one?

I'm ok with changing the `detachEventHandlersByType` parameter to a list, but I believe that `array.indexOf()` traverses the array each time, which isn't very efficient if it's wrapped in another loop.