composites now have generic multi add / remove methods
updated demo to use composite generic methods
reorganised demo for clarity
added Mouse.setElement
removed default MouseConstraint from engine, now must be manually added by user (see demo)
added default scale to sprites
constraintIterations now defaults to 2 for better stability
improved newtons cradle
delta is now sampled over 1s, improves stability
replaced "in" operator usage with access checks, it's a little faster
added catapult demo
improved constraint performance
added composite meshing and soft body factory
added cloth, soft body and bridge demos
updated edge build