add back/forward mouse button support for efm when a toolbar is present
add back/forward mouse button support for efm when a toolbar is present

button numbers untested because I don't have a mouse, so if they're wrong someone should post the results of clicking those buttons from xev

T67

rvandegrift/e,tasn/enlightenment,FlorentRevest/Enlightenment,FlorentRevest/Enlightenment,tizenorg/platform.upstream.enlightenment,tasn/enlightenment,tizenorg/platform.upstream.enlightenment,rvandegrift/e,tasn/enlightenment,tizenorg/platform.upstream.enlightenment,FlorentRevest/Enlightenment,rvandegrift/e