ids.cgi: Refactor reading-in rule files.

ids.cgi: Refactor reading-in rule files.

Move the code for reading and parsing the snort rule files
into an own subfunction.

* Drop code for reading in and modifying the snort main config file.
* Rework code for parsing and adding the snort rules to the snortrules hash.
* Drop code for gathering a description for the rule files, which does not
  because of a file layout change and sadly there is not suitable description
  shipped anymore by the snort team.

Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>