add vmware support in quantum

The existing nova-vmware-driver doesn't take care of vmware network management, which only deal with vm deploy from template or from vmdk.

The idea is to add a quantum vmware plugin, so that we can manage vmware networking inside openstack.

It will support both vmware vswitch and distributed vswitch.
Such as:
       create vswitch on an ESXi host, or create a dvswitch for a datacenter
       create network on vswitch/dvswitch...
       user should be able to configure vm networking via drag-and-drop while launch a new vm