Expose apply controller

vtkSMApplyController is a new class introduced for this project in the past. It encapsulates all the logic the Apply button does in ParaView but with no dependence in pq objects:

• Call UpdatePipeline on newly created sources
• Create (default) representations for those sources
• Update the view and reset the camera to the new data.

in this MR we expose the controller in Python and emit signals each time Apply() is called to allow the UI update itself if needed.

Although, it is reminiscent of the current button in ParaView there is no need to be manually called by the user. We could append it after each relevant interaction. See Remoting/Microservices/Testing/Python/TestWaveletContourPipelineWithRendering.py for an example.