Cleanup copy/pasta and use new codemirror-blocks toolkit API

[pcardune]

The only thing more satisfying than writing a bunch of code is deleting a bunch of code. This PR deletes a bunch of files that were never being used, and a bunch of other files that no longer need to be used with the new toolkit API.

TODO before this can be merged:

• Wait for the toolkit branch in codemirror-blocks to be merged: Implement toolkit API codemirror-blocks#374
• Figure out what the story is with css bundling. Currently it's bundled with the minified js bundle but sounds like it shouldn't be?
• Figure out what the story is with the "*-test-old.js" files in spec/ui as they are currently not being run.

[pcardune]

@schanzer couple questions for you:

1. what's the story with the "spec/ui/*-test-old.js" files? Do they need to run? Do they need to pass?
2. do we want to generate a blocks.css file during the build process? The code to do it has been commented out but it looks like wescheme.org is still loading one?