MDLSITE-2689 determine if coding style problems detected

I just use a checksum of the 'blank' file here to determine it, which is a
great big hack, but quicker than refactoring the checker at this stage.
MDLSITE-2689 improve the prechecker wording a bit

I'm hacking hacking hacking here..

* Capture the full job output using the jira client
* Grep that output to find out if the smurf file detected any problems
* Display a different message depending on the circumstances