WIP: Refactor JS into webpack sub-modules

[abelnation]

This is a WIP PR to demonstrate how I'd like to refactor the js code-base of pythreejs. I've only included a couple of modules to demonstrate the idea.

The reorganization would:

• isolate three.js objects to their own module
• put views and models for the same three.js next to each other
• remove require.js boilerplate code
• move towards commonjs style module require'ing

The index.js files in both the src dir and all subdirs can be automatically generated using the included scripts/write-index-files.js script.

@jasongrout @SylvainCorlay

[SylvainCorlay]

FYI, the examples directory contains js that assumes the THREE global variable exists as in old versions. This is why we defined THREE globally at the top of the jupyter-threejs file.

Besides, since we already go through a webpack bundling, one should be able to replace the amd style define syntax with a commonjs syntax in jupyter-threejs.js

[abelnation]

@SylvainCorlay If the number of three wrapped classes grows, it will be helpful to split them out to separate files, i.e. jupyter-threejs.js would get very very large.

I've removed the THREE requires from the submodules. The top-level index.js makes sure to require THREE and then set window.THREE.

[vidartf]

Is it OK to close this as outdated?