New stuff

* Admin interface that allows editing support tiers, organizations and donations.
* List of customers is now based on data in the DB.
* Prototype of the tiers page.
It does in the new form. See http://metabrainz.mbsandbox.org/admin/donationview/new/.
https://github.com/metabrainz/metabrainz.org/blob/new-stuff/metabrainz/model/donation.py#L28