0.260

- Added crackable planets. You can activate the "crackable planets" mode from the physics menu
- Added relativistic jet / beam in the customization menu
- Added neutron star surface in the customization menu
- Added "Darkstar aura" in the customization menu
- Added Customizable galaxy textures: you can now import the galaxy textures of your choice into the game. A good source are the images taken by Hubble: https://esahubble.org/images/archive/category/galaxies/