rpearce/grichards: Add support for persistent storage:

    * Fix regex's for lv data for vg function
    * Rename GB function as it uses KB not bytes
    * Convert output from du to GB
    * Ensure output from du is apparent size (as we thin provision vms when using Image, see ->
      * http://serverfault.com/questions/428868/does-kvm-raw-images-support-preallocation
    * Fix bug, init filesystem if newly created, not if !persistent
    * Modify computenodestorage to also return images and logical volumes.