mp4 cache

[minami110]

I've created mp4 or gif exportable Flipbook rendering node : Houdini

Also I discovered a bug where if you render out an mp4, delete the mp4, and then clear cache and then render again but cancel roughly half way through the render by hitting escape, a new mp4 will be created that has the first half of the new mp4 and the last half of the old mp4. Obviously this will only be noticeable if you change whatever animation you have between doing the two renders.
So either when a user cancels the render, no mp4 should be created, or at the very least the temporary files used to create the mp4 files should be deleted after each render/cancelled render.