Permanents trackers

Add the ability to make trackers permanent (not being able to remove them from /stattrackers)

**Describe the solution you'd like**
Add an option in the settings for each individual tracker e.g. stat.damage_dealt.permanent: true/false

**Describe alternatives you've considered**
Make trackers non-removable by default and add a permission to remove any of the trackers like stattrackers.remove
