reanimate clean task to remove orphans without rm -rf && acrylamid co

[posativ]

With an SSD it might be painful to rm -rf output/ and regenerate from cache. Due the new cache system, it might be possible to cirvumvent the previous issues. Also: the --dry-run infrastructure still exists.

This is related to #104 as it requires an API that forces all file creation/modified/skipped events to be routed through the event class.