fixed caching bug and related issues


I've also noticed that in CB code it is cache_image=False  so I've reset the GenericImage default's to False. ;)

It looks like it's working well now.


I think Jean-Luc is right -- you may have made a fresh fork, but somehow it's not been rebased against the latest code, because this pull request is incorrectly claiming to provide OffsetTimeFn, which is already in the codebase.  Please fix it so that we can see your actual changes, because we can't otherwise see what this pull request does...