Allow package_get by name

If package lookup by id fails, filter by fully_qualified_name
and choose the first (and what will be only) result. Also allows
delete and update to use FQN as well as ID.

This may need revisiting to allow non-unique FQNs.

Change-Id: I84fb8e155b5aa4bc036f8b598101b6b969962325
Implements: blueprint id-fqn-equivalence