Added more useful SmartOS Zone grains

Added the following fields to SmartOS grains:

 - pkgsrcpath      : Full path to the pkgin repo in use by the zone.
 - zonename        : The internal UUID of the Zone.
 - zoneid          : The internal ID of the Zone.
 - hypervisor_uuid : The UUID of the hypervisor hosting the zone.
 - datacenter      : In Joyent cloud shows the Id of the datacenter.