Added native function for OnClick Handling.

Native function wxOnClickView, handles view being clicked and sends it to wxWidgets.
WXView will now hold pointer to corresponding view.

This pointer value will be passed to event handlers in C++ in order to invoke them without searching for reference.
Added ptr argument to addView function.

WXView requies "long ptr" from now on, wxControl should pass it when it is constructed.
Added passing of ptr by button.

From now on every wxControl to get implemented needs to pass "this" as jlong. Reason for this is support of events and calling events from native functions.