Merge pull request #31 from yast/exception_handling

Do not hide libzypp exceptions in Pkg::ResolvableProperties()
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