New Zen+ difficulty and gameplay update

Hi all,

A new update has just dropped that adds a new difficulty level. Gameplay improvements have been made and a number of major bugs have been fixed:

Gameplay:
- Zen+ difficulty. More ships. +30% enemy HP. Good luck!
- Each player ship can now have only 1 Start Multiplier. This has been offset be increasing the value gained from the 'More Multiplier' perk.
- Ship stats have been re-balanced. This means most player ships should 'feel' better. However, because of the way the procedural system works, some ships might need a 're-roll' and therefore might change quite a bit.

Bug fixes:
- Hangar screen can now handle unlimited ships.
- Random crash on Game Over screen should now be fixed.

Stats:
- Press 'D' in the options screen will dump your high score data to the debug.txt file. Handy to find the tracks with the best / highest score rate.

A big thank you to Ceph and the players on the discord server for suggestions, feedback and testing.

Cheers,
Steve