Added new ServicesProposal library

- needed for bnc#887688
- Yast Network will have to set it (sshd)
- Yast Services Manager will have to read it and export it within its own configuration
- The test passes
- The package builds
No, but I like to current implementation more. Especially if you can find someone else asking why I haven't used a Hash instead of two lists. It's a matter of taste.