Implementation of second phase of provider extension.

Implementation of second phase of provider extension.

Enhances provider extension to support flat networks and VLANs on
multiple physical networks. Implements blueprint provider-networks.

To create a flat network using the CLI with admin rights:

net-create --tenant_id <tenant-id> <net-name> --provider:network_type flat --provider:physical_network <physical-network>

To create a VLAN network using the CLI with admin rights:

net-create --tenant_id <tenant-id> <net-name> --provider:network_type vlan --provider:physical_network <physical-network> --provider:vlan_id <vlan-id>

The provider extension is supported by the linuxbridge and openvswitch
plugins and their agents [openvswitch phase 2 implementation is
in-progress, and does not yet support flat networks or multiple
interfaces].

Ranges of VLANs available on named physical networks for normal
allocation are specified in the plugin's config file via the
ListOpt syntax:

network_vlan_ranges = <physical_network>:<vlan_min>:<vlan_max>

The mapping of each named physical network to its physical network
interface is specified (per-agent-host) in the agent's config file via
the ListOpt syntax:

physical_interface_mappings = <physical_network>:<physical_interface>

See quantum/plugins/linuxbridge/README for details and examples of
network_vlan_ranges and physical_interface_mappings usage.

Also, bulk operations are enabled for the linuxbridge plugin.

Change-Id: I93402bd5cc6316e9408ea71c3b3989d06898ee30