Fixed indentation.
Refactoring fix for bnc#476490
Fixed indentation, removed dead code and useless comments
Straightened dialog sequence for s390 Add/Eddit actions on interfaces

It also reimplements fix for bnc#476490.
Select reasonable defaults for s390 device variables. See bnc#747844
Replaced usage of LanItems::current by getter at couple places.
Updated changelog.
s390: renamed helpers, added constraints into helpers, small refactoring
Merge pull request #63 from mchf/bnc747844

Two related fixes for s390 Add / Edit device actions.