Use check_fortigate.pl plugins

I've juste rewrite this module in order to use the "check_fortigate.pl" plugins. http://exchange.nagios.org/directory/Plugins/Hardware/Network-Gear/Fortinet/check_fortigate-2Epl/details

This one allow to check Cpu and mem consumption both for master and slave router and it's now possible to monitor number of session.

The plugin used to check the fortigate is check_fortigate.pl and should be edited to set a "temp dir" (See share/libexec/check_fortigate.pl:71). Maybe it will be great to add this in the shinken "install -p" script.

Hope this will be usefull for more than me !