Service::GetUnitId and Service::GetServiceId utilities
Changed to use network.service alias link

Changed to use network.service alias installed by the NetworkManager
service file while "systemctl enable".
Obsoletes the use of the NETWORKMANAGER=yes/no sysconfig variable in
/etc/sysconfig/network/config (bnc#764055,bnc#764336,bnc#798348).
Updated changelog, version 2.23.20
Fixed to require sysconfig >= 0.80.0
Merge remote-tracking branch 'mtomaschewski/bnc798348'

Conflicts:
	VERSION
	package/yast2.changes
Merge pull request #51 from mvidner/master

Changed to use network.service alias link instead of NETWORKMANAGER=yes/no