Add Vagrant configurations for multiple different systems to contrib
Vagrant can enable us to have pre-configured VM blueprints with Tor development environment that developers could easily instantiate on their local machines.
We should have Vagrantfiles for:
* Linux (at least Debian, maybe some more).
* FreeBSD
* OpenBSD
* NetBSD
* Windows 10 (stretch goal)
* Android-x86 (stretch goal)
issue