Notes:
* Don't store the g2->g3 map in the task; it gets too large and
overflows the context column.
* Import album sort orders
* Try to treat duplication in the summary and description fields
sensibly.
* Move the g2 import config page under the Settings menu
* Clean up the settings page slightly and send users to the
maintenance page to do the actual import (not an optimal UI, but it
works).
around in the task so that on subsequent import runs we don't try to
reimport stuff we've already pulled in. This also gives us a mapping
so that we will be able to translate old G2 urls into the hot new G3
urls.
