Added event listener & event handler that will create calendar events upon creation of a new performance.

@todo: Currently the CreatePerformanceListener class implements ContainerAwareInterface & is passed an instance of the container. This is not a desired dependency as it costs too much overhead to create the object. Need to refactor code to de-couple the listener & handler from the container itself WITHOUT passing either of them an instance of the doctrine entity manager, which causes a cirucular dependency reference exception to be thrown.