Instead of displaying a fixed error message inside the yellow bar itself,
now the yellow bar disappears on error and a red compose_error is shown.
The error message is the one returned from the server.
This commit transitions all styles in app.css in the Django pipeline
to being compiled by webpack in an app-styles bundle, and renames the
various files to now be processed as SCSS.
To implement this transition, we move the old CSS file refernces in
settings.py and replace them with a bundle declared in
`webpack.assets.json` and includedn in the index.html template
Tweaked by tabbott to keep the list of files in `app.css` in
`webpack.assets.json`, and to preserve the ordering from the old
`settings.py`.
Cynthia Lin
Shubham Padia
Aditya Bansal
Armaan Ahluwalia