Fixed firewall proposal when using VNC

- There was wrong firewall configuration file used for VNC case
- bnc#892899
Changes and version
Merge pull request #236 from kobliha/vnc-installation

Fixed firewall proposal in case of VNC installation
ALWAYS require openssh / SuSEfirewall2 package depending on user decision

- and also depending on the defaults
- bnc#893126
Cleanup
Open or close SSH/VNC ports depending on user decision
Fixed using Firewall constants
Changes and version
As you wish, IDs -> ID
Merge pull request #237 from kobliha/sshd_and_minimal_sw_selection

Fixed selecting required packages (openssh, SuSEfirewall2) in case of default configuration + minimal sw selection
ifplugd package is not required. bnc#891517

ifplugd package is not present in SLE12. It was completely replaced by
wicked.
Updated testsuite for Lan::Packages
Lan::Packages - refactoring
Updated changelog
Merge pull request #235 from mchf/bnc891517-ifplugd-dropped

Do not insist on ifplugd package