COOK-760 - use attributes to determine the selinux state; also some additional enhancements

This pull request is based on j. timmerman's earlier work on COOK-760; that work is now completed.

This pull request includes some additional enhancements:

- The selinux type can now also be set.
- Triggers automatic relabeling when switching from disabled to other states.
- New recipe to install setroubleshootd.