Add a new cross platform example demonstrating rendering the environment to a texture. This texture is then used rendered to a full screen quad with a simple vignette post-processing effect for illustratation. Added a new optional method to the base IExample which is invoked prior to rendering the environment, to allow a hook to start rendering into the texture.
Remove using namespaces from implemetation, instead wrap in namespace directly -- review comment.
Experiment with implementing the RenderToTextureExample using the platform rendering types, based on review comments.
Remove types which were duplicating functionality provided in the platform rendering for creating a 2D quad mesh and associated vertex format.