Add proxmox terraform example

[Zempashi]

Add proxmox terraform example. This will be the foundation for the documentation (yet to come). This is levaring openstack image and cloud_drive cdrom instead of the standard cloud-init drive support in proxmox. This hack will hopefully not be needed in the futur when proper "proxmox" image could be issued.

How to use

Basically you need a proxmox cluster and mkisofs locally, and then follow the REAME.md in the proxmox sub-directory

Testing done

Spawning a instance on proxmox, destroying it.