Release 1.10: Enhancements and bug fixes

1) New music: At the start of the level, the mothership places new enemies. Now a mysterious music is played at the same time
2) You can now see the release number of the game in the main menu at the bottom right
3) After you have destroyed all enemies and the mothership spawns new enemies and you return to the main menu, the mothership continues to fly around in the main menu. This bug is fixed with release 1.10