Convert messages.less to CSS

For a performance improvement, we should convert messages.less to a CSS.

There are quite a few Bootstrap mixin calls in here (`.well`, `.alert-success`, `.alert-danger`, `.alert-warning`, `.alert-info`, `.border-top-radius`), plus a `floor()` on `@font-size-base`. The mixins need to be expanded by hand or replaced with their HTML classes, so this is not a trivial conversion.