Add new role 'embedded workstation' and several recipes

This is a 'work in progress' for a headless workstation that intend
to use to develop for Debian project and as file server.

New recipes included in this commit:

* chef
* dropbear
* easygit
* sudo
* vim
* virt-manager
Annotate to-do action in virt-manager recipe
Add nfs-kernel-server recipe
Add screen cookbook
Merge remote-tracking branch 'origin'