WIP: Introduce SSAO and ToneMapping

Create class vtkPVImageProcessingPasses inherited from vtkImageProcessingPass that encapsulates passes executed after the camera pass. For instance SSAO and Tone mapping is available, and adding new image processing passes should be easier with this class. The method SetDelegatePass is overridden to set the delegate pass of the first image processing pass after the camera. This is done by saving the first image processing pass in the update function.

Tone Mapping configuration : You can enable / disable tonemapping and choose the exposure coefficient in the properties panel of the render view. In the render view settings, you can select the tone mapping method, and if Generic Filmic is selected, you can use default presets (Uncharted2 or Default), or use custom parameters.

SSAO configuration : You can enable / disable SSAO in the properties panel of the render view. In the render view settings, you can choose the radius, bias, kernel size, and blur. As the radius and bias can be calculated from the bounding box of the geometry, you can select "Use SSAO default presets" to automatically find radius and bias.