v0.17.0: A minimal effects setting

Reduced effects made things lighter. Minimal makes them light.

Added

• Minimal effects, a third setting under Options. Reduced thins the particle work; minimal removes it. Exhaust trails and contrails stop, decoration is skipped, bursts drop to a single spark, and floating damage numbers switch off with the rest.
• Explosions and hit feedback stay on at every level. You should always be able to read what your guns just did.

Changed

• The effects setting is now three levels rather than a switch. If you had reduced effects turned on, it stays on.