Core: Move FormationMgr to namespace

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

src/server/game/Spells/Spell.cpp

@@ -843,6 +843,8 @@ void Spell::SelectEffectTypeImplicitTargets(uint8 effIndex)
             if (targetMask & TARGET_FLAG_UNIT_MASK)
                 AddUnitTarget(m_caster, 1 << effIndex, false);
             break;
+        default:
+            break;
     }
 }