Allow players to track both herbs and minerals at the same time

PR as [requested](http://www.trinitycore.org/f/topic/9390-patch-allow-track-herbs-and-minerals-at-same-time-updated-22-11-2013/#entry68082)

__Note:__

For documentation sake, [here](http://www.trinitycore.org/f/topic/9390-patch-allow-track-herbs-and-minerals-at-same-time-updated-22-11-2013/#entry61754) is a useful macro to allow players to toggle both trackers on / off. Just open the spoiler in the post.
If you have one tracker active and activate another, it has to return FALSE if the config isn't set otherwise the check for specific stack rules screws things up and Hunters can track everything.