Update to latest ShaderParticleEngine release (0.7.5)
Incorporate ShaderParticleEngine#rebase_spiral branch commit

Adds 0f60b7e8f7db440685eba8b92150f245a7e7415a to SPE,
adding spiral type emitter to library
UI: Add maxBuldge parameter to spiral emitter properties
UI: workaround for SPE issue #49 allowing < 1 particles per sec
UI: use updated SPE library for system interconns and star dust

Slightly tweaked / updated effects
UI: update update SPE lib for galaxy particles / add center

Improves galaxy effect by diversifying the particles emitted
and adding a central 'black hole'
UI: randomize bg in / add star-dust to dev.js
UI: s/eulerOrder/rotation.order in canvas scene mixin

Gets rid of three.js deprecation warning
UI: add particle effect to system gfx

Tweak to system position constraint + use alternative png
for solar system plane
UI: Use new ShaderParticle API / Classes in effects