misc-progs: getipstat: Refactor + extend

misc-progs: getipstat: Refactor + extend

* Return output of iptables directly instead of writing it to files.
 * Make iptables wait for 5s if xtables is locked by another iptables
 process. (--wait 5 argument)
 * Add optional parameter "-x" to have iptables report exact numbers.
 * Add optional parameter "-f" to display  the filter table  (default).
 * Add optional parameter "-n" to display the nat table.
 * Add optional parameter "-m" to display the mangle table.
  * Adapt iptables.cgi and guardian.cgi to catch getipstat output
  instead of reading temp-files.

Signed-off-by: Robin Roevens <robin.roevens@disroot.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>