added asteroid explosions
explosions expand from blast point in predictable trajectory
using vertex colors for particles, animation duration long
explosion particles gradually lose opacity
explosion class' only dependency is global THREE object, configurable
opacity increased at end of explosion animation
object pool util class added
optimizations for explosion loop
added global registry object, object pool can 'collect' and delete
object pool calls obj.initialize with firstAlloc as last param
stage, physics are globally available from registry
reorged directory structure
easy collision event subscription for actors
improved custom events, explosion controller added
started work on using Sparks.js for ship exhaust particle effect
removed SPARKS, added performance stats monitor
removed Actor as possible instance, should be abstract
generic object cloning, added asteroid controller (unfinished)
using verold supplied update event handler for main game loop
explosion now using verold update event for animation