VF Auto Save Render 1.7.3

Adds {collection} to the available dynamic variables, re-institutes the ability to track total time spent rendering in an external text file (perfect for tallying entire projects as you work), and adds support for dynamic variables in the Compositing tab when using a File Output node. There are some limitations to this new feature (it only supports a single node), but it should work nicely for some compositing pipelines.