* systemd: use PrivateUsers= in user unit
ProtectSystem= and other sandboxing options require a user namespace in
order to work as user units (the user manager does not run as root and
thus without a user namespace it is unable to perform mounts).
* Move lots of stuff into contrib directory to clean up root folder
* Update autoconf files for new location of some files
* Refactor README split and move to docs directory
* Update INSTALL.md
* Update Makefile.in
* Install docs from new location
* Uninstall docs correctly
* Update Dockerfile
* Fix up Dockerfile spacing
* Move systemd stuff to contrib
* Move docker specific stuff to contrib/docker, update docs
* Fix Alpine and Stretch docker files
* Update configure after changed file locations
* Update INSTALL.md to include pkg-config as requirement
* Move also entrypoint.sh to contrib/docker
* Update 'min-notif-changes' to 'min-notify-changes' which was missed in PR #467
* Update to add --sync-root-files to usage.md and man page
* Update usage.md to include --auth-files ARG details
