Headless rendering support to disable chunk reloading for multiple scenes with same chunks

This would be a difficult to implement feature but for batch rendering a must-have.

When you have a lot of chunks selected and want to render multiple scenes with these chunks, using headless rendering, you have to reload all the chunks every time. This is because every scene .json file is seen as a different render even though they have the same chunks selected.

Currently using the normal program you select your chunks and you can render multiple scenes with them, having to load them only once. If this was possible using headless rendering it would save a lot of time.