Add ssi contrib file to turn tickets into links

This is a sample ssi file that can be used as an example on how you can
transform ticket numbers (or whatever regex you want) into a link to an
internal ticketing system.

This works on the host/service information pages as well as the
comments/downtimes pages. It has been tested in Chrome, Firefox, Safari
and IE.

Did some testing here if it is at all useful:

http://jsfiddle.net/mj03xe5y/12/