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)

* Merge note: cherry-picked from 117a9d6f5d4ea2df2eb66bd8537db0034b4c5bca
  and adapted to maint-1.0 branch.

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>