Update Thumbslug to use systemd.

Additionally:
- Use the jpackage_script macro to build the wrapper script for us.
- Add attrocious SELinux policy version hack.
  See https://fedoraproject.org/wiki/SELinux_Policy_Modules_Packaging_Draft#Runtime_Dependencies
- Install thumbslug in the normal place for JARs.
- Build a proper jar repository. Don't just use everything in /usr/share/java.
- Add some SysVInit requires when not using systemd.
- Use %{buildroot} macro.  It's shorter.
Update thumbslug shell script to use jpackage-utils

This script is now very similar to what the %jpackage_script RPM
macro produces.
Put configuration files in their own directory.