Initial support to load rules from a remote server

New directive `SecRemoteRules' was added. It allows the user to load a
set of rules from a given HTTP server.
Adds the SecRemoteRulesFailAction directive

This directive allows the user to set a default action whenever the
SecRemoteRules failed to download a set of rules. Current the supported
values are: Warn and Abort. By default `Abort' is selected.