Break up the JavaScript monoliths

Right now, the JavaScript code for CodeWorld is split between two monolith files: codeworld.js and codeworld-shared.js. It's not even clear to me what goes where, or how either file is really organized. I'd really like to see things divided into main modules by functionality:

1. The core functionality around the UI.
2. All the project management stuff: loading, saving, moving, deleting, etc. projects and folders. Nothing here is called unless you're signed in.
3. The editor functionality: setting the code, error highlighting, doc popups, formatting, autocomplete, etc.
4. The output window, where errors and debug output appear. Currently, this is pretty simple, but I really want to make the output area more feature-filled, especially in Haskell mode (supporting stdin would be great!) So the organizational choices should plan for expansion here.

This is in addition to things that are already part of their own files: the inspect UI, the Guide, etc.

See #66