bugfix for 613
Merge pull request #626 from surface-smoothers/fix.613

bugfix for ticket 613
fixing f3149e13175bee0d8ebd2653e9c18f2b0496ddbb (tr.613)
tests: print(ring/qring)
bugfix in reduceZ
Merge remote-tracking branch 'smoothers/fix.reduceZ' into spielwiese.patched