Editor improvements

[ErlerPhilipp]

A few annoying things to resolve:

1. No automatic reloading: if editor is empty, "press" reload button automatically every ~1 minute
2. After loading reconstruction result, the mesh is just black until the camera is updated: update rendering once when texture loading is done
3. Objects are almost always upside-down (COLMAP seems to have a strange/different coordinate system): flip up-axis of reconstruction result so that it is upright in editor and downloaded mesh
4. Editor screen is completely empty in the beginning: Start with a nicer camera angle of e.g. 45 degrees looking down onto the object