[ansel] Using datatree_id to reference galleries

[Ben Chavet]

> Ah, you're right. It'd be much simpler if we just stored the
> datatree_id in that
> field, since that would never change - that way the move would be automatic.

I'm not sure why, but when I started using the datatree_id instead of the
datatree_name in the 'gallery' attribute, postgres would choke on the 
query.  I
waited a good 10 minutes & it was still pegging one of my processors.  Here is
the query:

SELECT a1.datatree_id, c.datatree_name FROM horde_datatree c LEFT JOIN
horde_datatree_attributes a1 ON a1.datatree_id = c.datatree_id WHERE
c.group_uid = 'horde.shares.ansel' AND (a1.attribute_name = 'gallery' AND
a1.attribute_value = 2822) AND a1.attribute_name = a1.attribute_name ORDER BY
c.datatree_order, c.datatree_name, c.datatree_id

There was only 1 image in the gallery, not sure what was killing it.  The only
difference from using datatree_name is the a1.attribute_value = 2822 
instead of
a1.attribute_value = 'some_gallery_name'.

This query is a bit above my head, so does somebody with better SQL knowledge
have any idea?

--Ben