Better embeddable editor

It's possible to embed CodeWorld into an iframe in a larger page. However, it's not a great experience currently. The page loads a sidebar with currently open projects that you can swap through, auto-runs any code that's loaded into it with a new pane on the right, and cannot be controlled at all from the parent frame. We can do better.

Ideas here:

1. Have a kind of URL that loads code into JUST an editor. There should be options to disable all the extras, like the project browser, auto-run, even the Run button at all, etc. There should be an option to make it read-only if desired. Possibly there should be options to customize the styles to match the parent frame. An optional button to pop out into the full CodeWorld environment in a new tab would be nice, too.

2. Define a protocol for the CodeWorld editor to communicate with its parent. For example, the parent frame should be able to send the editor commands to scroll to a location, and highlight a range of the document. The parent should also be able to intercept the Run command so it can run the program in a different location instead of popping out from the right side of the page.