Refactoring NetworkInterfaces helpers for parsing ifcfg device names.

These helpers are partialy incompatible with new naming scheme.
Fixed comments.
Fixed deleting alias assigned to device with new style name. bnc#846550
Removed some YCP -> Ruby artifacts
Updated changelog
Created rspec test for NetworkInterfaces ifcfg device name helpers

Purpose is mainly to cover current state regarding old even new
naming scheme.
Merge pull request #120 from mchf/bnc846550-deleting-aliases

NetworkInterfaces: Make handling aliases compatible with new naming scheme