Add passingt est for adding a Term to an Item
Add unicode methods for Taxonomy and Term
Change the unique contstraints for Term so that
Term name needs be unique only for a given Taxonomy

Removed taxonomy and term classes from data_layer - just reference the ones
in taxonomies app directly for now.

Will need to run "deploy/tasks.py clean_db" and "deploy/tasks.py update_db"

Tidy up transport delete items

Make the url generation work proerly (though I'm fairly sure we don't
actually need the url as an argument to delete) and remove
debug print statement *blush*

These are no longer used by transport, and nobody else should be using
them.

Note: transport still uses the explicit views

tests broken

byepassing data_layer.handlers, but I think they are
getting in the way of DRF goodness now.