Final battle system and more

Got another chunky update! This one adds a bit of a climactic end to the entire game so far.

Content:

• A new final showdown system: when you save enough planets you will be taken to a system where the enemies are making a final stand. Here you can set up defenses to help when the final fleet arrives. Defeat the fleet to drive them out of the region for good.

• Reworked the Ninja Star ability a bit. It spawns more Ninja Stars, they can destroy incoming projectiles to help protect the ship more and they can be released without spawning more instantly.

• Update to HUD display, ammo and health now float near the player's ship to help keep that information easy to see.
• Fixed bug where events would spawn immediately after you are paused
• Fixed a crash when a planet was reduced to 0 health @Max reported
• Slightly smaller hitbox on player's ship (should make the game a little easier)
• Added damage indication when enemies or the player are near death