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>