Pkg::TargetInitDU() - added new parameters (bnc#896176)

- added optional "growonly" and "filesystem" parameters
  to better handle Btrfs partitions with snapshots
disk usage - do not silently ignore libzypp errors
changes

- 3.1.19
comment the default values
Merge pull request #32 from yast/partition_api_update

TargetInitDU() - added new parameters (bnc#896176)