Finish off rebranding of the Nicira NVP plugin

Old names are kept for backward compatibility.

Last references to the old NVP plugins are going
to be dropped in Juno.

Completes blueprint nicira-plugin-renaming

Change-Id: Ia1aa4f658891e7ce9469748432c338353195edfd
Merge "Finish off rebranding of the Nicira NVP plugin"