Improve reporting of pre-checker results in the Tracker

Right now we are deciding about the status/results to be shown in the tracker based on a hash-hack.

With the changes performed @ MDLSITE-3422 now it's possible to kill such a hack an improve notifications in the Tracker by:

• using the individual and grand counters now available.
• modifying the bulk-precker to access to that information and decide, for every check, if it's a pass, a warn or an error status.
• send all that information to the tracker.

That is it, ciao