object-ify flavors api and compute/api side of RPC

This change converts flavors to use objects instead of direct database
access. The rpcapi primitivizes objects before they go over the wire.

The flavors.add_flavor_access() and flavors.remove_flavor_access()
functions were also removed as flavor object add_access() and
remove_access() should be used instead.

Related to blueprint kilo-objects

Change-Id: I86432720b600e479d8d8b7f7531a2c85ab364319
Merge "object-ify flavors api and compute/api side of RPC"