pybullet: allow to replace existing text, to avoid flickering (remove/add)

allow texture caching (disable using the disable file caching)

examples/Importers/ImportURDFDemo/BulletUrdfImporter.h

@@ -9,7 +9,8 @@ struct BulletURDFTexture
 {
 	int m_width;
 	int m_height;
-	unsigned char* textureData;
+	unsigned char* textureData1;
+	bool m_isCached;
 };