[ansel] Ansel::listGalleries()

[Ben Chavet]

> Do you intend to allow a user to have the same image in multiple
> galleries?

Probably eventually, but that will be a different project for me.

> Any deletion from a gallery would
> just remove the link and not the actual image (thereby avoiding the
> reference count issue).

Or, when an image is deleted from a gallery, check if it is in any other
galleries.  If not, just delete the image.

--Ben