Changes

Fix NPE if NPC removed without spawning
Update players based on navigating NPC's. Update player when NPC
navigates into players field of view.
Moved skin update tracker code to own class (SkinUpdateTracker)
fix use incorrect setting for tab list
rename PlayerListRemover to TabListRemover
rename recently added NMS#sendPlayerListRemove, #sendPlayerListAdd
methods to #sendTabList*
 (commit: 5e3547d)