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>