Add V3 api for pci support

All pci passthrough code is merged into nova, but the APIs are not supported.
This patch provides a resource: endpoint to show PCI information. This is a
part of PCI APIs, for more information see the blueprint.

Partially implement blueprint pci-api-support

Change-Id: I05c502cb7564b8b71f12d8f06249124b3d2b370f
Merge "Add V3 api for pci support"