Implemented item frames, a part of #689

+ Implemented Item Frames
* Fixed Pitch and Yaw being wrongly flipped in the protocol (XOFT!)

src/WorldStorage/NBTChunkSerializer.cpp

@@ -627,6 +627,7 @@ void cNBTChunkSerializer::Entity(cEntity * a_Entity)
 		case cEntity::etProjectile:   AddProjectileEntity  ((cProjectileEntity *)a_Entity); break;
 		case cEntity::etTNT: /* TODO */ break;
 		case cEntity::etExpOrb: /* TODO */ break;
+		case cEntity::etItemFrame: /* TODO */ break;
 		case cEntity::etPlayer: return;  // Players aren't saved into the world
 		default:
 		{