Fixed selecting required packages (openssh, SuSEfirewall2) in case of default configuration + minimal sw selection

- Packages are now requested always
- Opens/closes ports as requested by user
- bnc#893126
- includes a little refactoring
- no test case, that require to put everything into lib/network (in TODO)
- tested in production

Um, you can actually use `:symbols` or even integers. The advantage of the constants is that you'll get an exception when you make a typo.

With symbols you won't notice that you used `:enable_ssdh` instead of `:enable_sshd`, the dialog will be displayed but something won't work as expected...