Various updates

Just putting out another update with the following changes:

• Changed the way caching of the GPUParticles/Shaders works to reduce visible lag spikes
• Changed some particle effects from GPUParticles to CPUParticles this really helped stabilise fps on low end devices(*1)
• Trimmed about 3MB off of total game size
• Made the game a little bit easier

I think these changes will address some of the major performance issues, especially on low end devices or computers with integrated/onboard video cards.

*1 - In Godot it seems as though particle effects with a low number of particles run much better as CPUParticles vs GPUParticles.