Asteroid Fixes

NOTE: Leap scripts and the Box Collider for the ship are probably
unticked in the editor, turn them back on!

- Asteroids now spawn in a sphere around the player, radius of sphere
specified by a single variable on AsteroidGeneratorBoxScript
- Asteroids will now no longer spawn inside the launch tube (The initial
spawn has a condition where asteroids are unable to spawn within a
certain distance of the player)
- Asteroids also cannot spawn when the player is near the planet (fixes
hyperspace asteroids and asteroids flying in/out of the planet)
- Asteroids now fade in/out when they leave the spawning area to reduce
the effect of pop-in
Added Leap Motion Controlled Cubes in Cockpit