vagrant: Provide basic Vagrantfile

vagrant: Provide basic Vagrantfile

This is a basic Vagrantfile which compiles and provisions the local OVS
source tree in a Fedora 20 VM. The Vagrantfile.in can be extended to
support additional distributions.

To use this Vagrantfile:
 1. Install Vagrant plus a compatible hypervisor
 2. Run configure to translate Vagrantfile.in to Vagrantfile
 3. Run `vagrant up` to create & provision the VM
 4. Run `vagrant ssh` to log into the VM

Signed-off-by: Thomas Graf <tgraf@noironetworks.com>
Acked-by: Kyle Mestery <mestery@mestery.com>