GJP-51: let mouse wheel event get passed to mapController

Needs vote.

example: http://dev.geomajas.org/geomajas-project-javascript-gwt2-example-GJP-51_wheelEventToMapController/examples/default_controllers.html#

deselect navigation and select navigation again. compare with http://dev.geomajas.org/geomajas-project-javascript-gwt2-example-1.0.0-SNAPSHOT/examples/default_controllers.html#