- Provide an implementation for buildPool and deletePool operations
   for the ZFS storage backend.
 - Add VIR_STORAGE_POOL_SOURCE_DEVICE flag to ZFS pool poolOptions
   as now we can specify devices to build pool from
 - storagepool.rng: add an optional 'sourceinfodev' to 'sourcezfs' and
   add an optional 'target' to 'poolzfs' entity
 - Add a couple of tests to storagepoolxml2xmltest