This change adds the database models and API, as well as RPC objects
for the allocation API. Also the node database API is extended with
query by power state and list of UUIDs.
There is one discrepancy from the initially approved spec: since we
do not have to separately update traits in an allocation, the planned
allocation_traits table was replaced by a simple field.
Change-Id: I6af132e2bfa6e4f7b93bd20f22a668790a22a30e
Story: #2004341
Task: #28367