Add Contact, Address, User, Profile, and SOCOrganization to clear_db.
Add Contact, Address, User, Profile, and SOCOrganization to clear_db.

This enables clear_db to remove all entities seeded by seed_db. A conditional
is added to the actual delete operations to determine whether the entity is
an ndb.Model subclass and consequently needs to have delete called on the
instance's key and not the model itself.

rhyolight/nupic.son,rhyolight/nupic.son,rhyolight/nupic.son