Split the details of the fluid simulation off into a separate class, to keep the ofApp code managable, and because we will be adding additional effects as well, and these need a place to live too.
Also added a first start for a particles-effect that glows and is rendered on top of the fluid with additive blending. Had to make a change to ofxFX for this, since this module enables Alpha blending in its draw function, which is not what we want.