Include link to local application instance in comment "signature"

This will produce something like:

*You may blame the <a href="https://github.com/joomla/jissues">J!Tracker Application</a> at <a href="http://jtracker.local/">http://jtracker.local/</a> for transmitting this comment.*

which includes a link to the "local" application instance (which will be, of course, http://issues.joomla.org on "our" product)