Core: Move FormationMgr to namespace

Also...
- Warning fixes
- Make Singleton constructors private

src/server/game/Globals/ObjectMgr.h

@@ -1191,8 +1191,7 @@ class ObjectMgr
         void LoadFactionChangeSpells();
         void LoadFactionChangeReputations();
 
-    protected:
-
+    private:
         // first free id for selected id type
         uint32 m_auctionid;
         uint64 m_equipmentSetGuid;