Huge commit!

Note to myself: commit more frequently and each feature separately...

Changes:
* New model: jump gate
* Jump Gate object implementation
* Targeting planets, jumpgates
* Score system: points for asteroids, pickups and reaching the jump gate on time
* Displaying a highscore in the HUD of the menu
* Highscore saving/restoring for all time high scores
* Menu mode: closer to the planet with no asteroids around, use the jump gate to start the game
* Lag skipping
* Reuse asteroids instead of just asteroid names
* Exact position request usage for collisions
* Land on Earth to exit the game