Improved bit depth/compression options for CXR

When using CXR as the image output format, the entire image is saved as an uncompressed 32-bit image. In many cases this results in an astronomical file size that takes a long time to save, when most uses only require 32-bit.

It would be incredibly useful for the user to be able to define the bit depth (32 bit float, 16 bit float) and compression (ZIP, ZIPS etc.) for each render element - much like you can in the standard 3DS Max EXR setup.