*: Move all systemd service files from /lib to /usr

This is now the preferred location in Debian. See:

https://lintian.debian.org/tags/systemd-service-in-odd-location
https://bugs.debian.org/992465
https://bugs.debian.org/987989
d70caa69c6
https://lists.debian.org/debian-devel/2021/08/msg00275.html

Tests:

- Lintian no longer shows errors:
  E: freedombox: systemd-service-in-odd-location lib/.../calibre-server-freedombox.service

- Comparing the old .deb and newly generated .deb with these changes. All the
systemd files show that they are moved from /lib to /usr/lib/systemd.

- After upgrading the deb from older version to a version these changes,
services installed by the package are available (tested after restart with
wordpress and claibre). Services tweaked by the package have the changed
configuration reflected as shown by systemctl show
{service-name}.service (tested after restart with quassel).

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

debian/freedombox.install

@@ -1,5 +1,4 @@
 etc
-lib
 usr/bin
 usr/lib
 usr/share/augeas