Blender Git Loki

Cycles: Implement multi-frame buffer support and loading in standalone mode

This commits adds an option to the BufferParams that specifies how many frames are stored in there.
The frames share all other parameters, such as size and passes.
Frames are not stored in order - instead, the first frame is the primary frame, so that all code that uses
the RenderBuffers still works as expected, but code parts that can use the additional frames may do so.

The Standalone Denoising mode now comes with an option to specify the frame range that will be used for denoising.
When doing so, the input filename isn't an actual file, but has to contain a part of the form "%Xd" that specifies how the frame file names are formatted, where X is the length to which frames are zero-padded. That part will be replaced by the padded frame number before loading.

So far, no code actually uses the additional frames yet, that will come in the next commits.