[Request] Add FortiSwitch support from Fortinet.

[tkrause]

DO NOT DELETE THIS INFORMATION.

Please read this information carefully.

• Is your install up to date? Updating your install
  Please do not submit an issue if your install is not up to date within the last 24 hours or on a stable monthly release.
• Please include all of the information between the ==================================== section of ./validate.php.
  LibreNMS Version: 49db00b
  DB Schema: 148
  PHP: 5.5.9-1ubuntu4.20
  MySQL: 5.5.52-MariaDB-1ubuntu0.14.04.1
  RRDTool: 1.4.7
  SNMP: NET-SNMP 5.7.2
• If you would like us to add a new device then please provide the information asked for here
  Discovery - http://pastebin.com/6VSnaHrE
  Poller - http://pastebin.com/zghmMDiq
  SNMPBulk - http://pastebin.com/Tc7b99cj
  The device is a FortiSwitch from Fortinet which currently shows as a Generic device
• Please provide as much detail as possible.

The MIBS can be found here http://pastebin.com/hcrnYPKa