Bugfix for job cancellation (reported by Carsten in email)
Ended up recoding part of the communication pipe (use json more consistently)
Fix bpy data modifications where it shouldn't happen (as a bonus, thumbnailing is now done out of process)
jpeg versions of the render results are downloadable from the web interface.
Notes:
1) They are generated (and written to disk) on demand on the master in the same Blender instance, so this will increase memory usage (until there's a way to free and image buffer from memory or it's run in a separate process).
2) They are darker then the real results, since multilayer exr contain the result before gamma correction (for the linear workflow) and that's not applied when loading them as an image.
3) They are NOT thumbnails, they are the same size as the results (albeit at 90% quality jpeg compression)
Slave and Master options to delete files when closed (default True for slave, False for Master)
Web interface option to remove files (on master) when deleting a job (or all jobs)
Web interface button to pause a job
