Stuff that needs fixin':
 * think about where to cache objects in the Context. currently happens in
   constructors, but should maybe happen elsewhere (should objects be
   responsible for cacheing themselves? probably not).
 * CommunityDAOTest sometimes hangs for no apparent reason during test runs.
   Could be a db connection thing, but it should be investigated.
   A few others (MetadataFieldDAOTest, WorkspaceItemDAOTest) could potentially
   be suffering from the same problem, which suggests it's probably a general
   issue with connection pooling or some such.
 * Bar.addFoo() vs. BarDAO.link(bar, foo). We need to *either* use the
   link/unlink/linked methods of the DAOs (where they exist) *or* use the
   add/remove methods of the "parent" objects. I'm personally in favour of the
   former because it means we don't hold more in memory than is absolutely
   necessary, and the data layer is always up-to-date. It also removes the
   responsibility for objects to know what is associated with them.
 * Update the clean-database.sql script to account for all the new tables &
   sequences
 * After approving a workflow item, it says "...has been assigned the following
   identifier" and then gives the URL. Either change the text, or change the
   link to the actual identifier.
 * Need to forward requests from <url>/handle/ and <url>/bitstream/ to the new
   URI servlet, and have it mimic the previous behaviour.
 * Need a way to import items (and any other 'content') that have existing
   UUIDs / identifiers. One approach would be to just add the value of the
   identifier as a dc:identifier.uri, but that's not ideal.
 * When a Collection is deleted, should any WorkspaceItems that are being
   submitted to that Collection be deleted?