download ET IDS rules via HTTPS

download ET IDS rules via HTTPS

The Emerging Threats ruleset server supports HTTPS. It should
be used for downloading the ruleset in IPFire, too.

This also needs to be applied on the upcoming ids.cgi file for Suricata
which I will do in a second patch.

The third version of this patch superseds the first and
second one which were broken due to bugs in the MUAs GPG
implementation.

Signed-off-by: Peter Müller <peter.mueller@link38.eu>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>