Can zoom in and out in third person view.
Third person zoom - fixed code review issues.
Merge remote-tracking branch 'kolek/thirdpersonzoom'
MWMechanics::DynamicStat: fix members initialization
Calculate NPC health on loading instead of updating it continually

Only NPC with auto-calculated stats are concerned.
Move some levelup logic from mwgui to mwmechanics
Complete health increase on level up