Fixed checking whether SuSEfirewall2 is selected/installed

- in inst_sys, the package is already installed, although it's the first stage
- bnc#892935
Changes and new version
Merge pull request #287 from kobliha/detect-installed-firewall

Fixed checking whether SuSEfirewall2 is selected/installed
Sanitizing metadata got from SuSEfirewall2 services files

- bnc#893583
- Some maintainers use the TEMPLATE file to create their own service
  file, but they do not change some parts of the file, thus Yast shows
  texts like "template service" and "opens ports for foo in order to
  allow bar"
- this commit makes such texts ignored
Fixed reading service files

- Some used comments with leading '###'
Lazy-loading SuSEfirewall2 services

- bnc#872960: Services can be installed while Yast is already running
  (and thus SuSEfirewall can be read already)
- This makes Yast to read the services ONLY when they are needed
  (already handled internally in SuSEFirewallServices)
Changes and new version
Merge pull request #288 from kobliha/susefirewall-services

Fixed SuSEfirewall2 services behavior