Now when jittering is on it uses a shared noise texture
from the renderwindow for all mappers and is 64x64 in size.
This cleans up a lot of code and has a smaller memory footprint
etc.

A bunch of tests included OpenGL2 headers when they didn't
need to, so fixed those.

Other tests need OpenGL2 but are in RenderingVolume so moved
them into RenderingVolumeOpenGL2 where they should be.