Add a color to the selected mesh / Add different types of meshes (i.e. type#A or type#B)

```
What steps will reproduce the problem?
1. Go to JSC3D.Viewer.prototype.mouseDownHandler
2. Add
if(this.onmousedown) {
var info = this.pick(e.clientX, e.clientY);
this.onmousedown(info.canvasX, info.canvasY, e.button, info.depth, info.mesh);
//testing - add a point or mesh to the clicked point or mesh
var newMat = new JSC3D.Mesh.Material('', 0, 0x000080, 0, true);
info.mesh.setMaterial(newMat);
JSC3D.Viewer.update();
}

What is the expected output? What do you see instead?
The color of the selected mesh should change; nothing does get changed

What version of the product are you using? On what operating system?
latest version of jsc3d as of jan 27'15

Please provide any additional information below.
Type A would be the center of the entire image
Type B would be the center of masses (i.e. head, leg, body, etc)

```

Original issue reported on code.google.com by `jhicob...@gmail.com` on 26 Jan 2015 at 5:57

Start at JSC3D.Viewer.prototype.mouseDownHandler and inspect the existing pick result, Mesh.Material usage, and Viewer.update call. Determine how selected meshes should be recolored and clarify the intended Type A and Type B mesh grouping before implementing; done means the selected mesh visibly changes color and the requested mesh types are distinguishable.

Written by the indexing model from the issue text.