Additional spec file and config fixes

This release contains fixes from #8:

• Reduce the dependencies for the unauthenticated xrootd
• Create the config and systemd unit files during the make install process
• Tidy the stashcache configuration
  • Reduce the default disk usage of the cache to 90/95% to avoid
    accidentally filling filesystems too full
  • Move the certificate configuration inside the auth instance of xrootd
  • Set pfc.ram 7g to allow a bit of room for the OS on 8GB system
    (documented minimum RAM)
  • Added pss.origin redirector-itb as a commented line, rather than adding
    a separate itb config file

Make install fix and spec file update

• source files updates and spec file revision
• add LICENSE file

Major rework of retired stashcache-daemon-historic

Restructure of StashCache-Daemon, StashCache-Cache-Server, StashCache-Origin-Server.