[openvz|compute] Initial commit

This implements an openvz provider. This is a driver similar to vmfusion & virtualbox.

It includes:
-  a documentation : https://github.com/jedi4ever/fog/tree/openvz-provider/lib/fog/openvz
- a basic set of tests for the lifecycle

Merge at your leasure - 
Ping @fnichol , @skottler