installation: support for Apache-2.4

* Enhances `--create-apache-conf` to detect if Apache-2.4 or later is
  used and produces compatible configuration WRT directory restrictions.
  (addresses #1552)

Reported-by: Nedko Nedkov <nedko.stefanov.nedkov@cern.ch>
Signed-Off-By: Samuele Kaplun <samuele.kaplun@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>