actors might need stage events (clear/load???)

[sphaero]

The python actor needs to update paths when it gets loaded and needs to unload paths when the stage gets cleared.

The working dir is not enough for python modules in a stagedir

So when stage gets loaded add <stagedir>/pythom-modules/ to sys.path. When stage gets cleared remove <stagedir>/pythom-modules/ from sys.path.

An actor could also use a register function. Check dynload for this