PyCEGUI should be able to subscribeEvent with a callable

Issue #454 resolved
Martin Preisler
created an issue

Right now you have to use an awkward way to subscribe.

it should be possible to do this: widget.subscribeEvent("EventName", otherInstance.someMethodOnIt)

istead of widget.subscribeEvent("EventName", "someMethodOnIt", otherInstance)

Reproducibility: N/A