implemented image format registry

src/engine.cpp

@@ -182,6 +182,7 @@ Engine::init(void)
 
 	// core plugin attach here
 	Frame::registerModule();
+	Image::registerModule();
 	Raster::registerModule();
 	Texture::registerModule();
 
@@ -279,6 +280,10 @@ Engine::start(void)
 
 	engine->device.system(DEVICEFINALIZE, nil, 0);
 
+	// Register some image formats. Or should we leave that to the user?
+	Image::registerFileFormat("tga", readTGA, writeTGA);
+	Image::registerFileFormat("bmp", readBMP, writeBMP);
+
 	Engine::state = Started;
 	return 1;
 }