Add Vagrantfile for OVSDB Test/Dev environment

This commit adds a Vagrantfile to the root of the repository. This
allows a developer to issue a single command to pull up a development
and test environment:

    vagrant up

This will create 3 x VMs in Virtual Box. VMs can be
created individually if required.

1 x VM for Mininet - 2GB RAM
1 x DevStack Control/Compute node - 4GB RAM
1 x DevStack Compute node) - 4GB RAM

See README.Vagrant for full instructions

Change-Id: Ieaaec6cde09ce9ecc7b31861f86695c662849f7d
Signed-off-by: Dave Tucker <dave@dtucker.co.uk>
Merge "Add Vagrantfile for OVSDB Test/Dev environment"