TNL-4692

1. Fix the broken `gettext()` call in `courde_detail.js`
2. Change the string to avoid Transifex misunderstand the pattern '% o' in `checklist.underscore`.
3. Embed the `{filename}` part inside the string in `transcripts-choose.underscore` to provide better i18n flexibililty.
4. Remove all the call of `gettext()` and `${_()}` inside the `mock` directory to aovid mis-extraction by pybabel. (It seems that the `mock` directory is soly used in test? So the strings in this directory need not to be extracted and translated?)
5. The unicode char `\u2014` will trigger a bug inside pybabel which makes the extracted string untranslatable, so remove this char.

* updating vendor files
* updating class syntax (to new FA-based classes) for all UI elements
* correcting broken tests

TNL-46

I've changed Studio to catch JavaScript errors when rendering xblocks, log the error, but to then continue as normal. This means that the user is still able to interact with the xblock to delete, duplicate etc. This seems reasonable as the xblock is only rendered as a WYSIWYG representation so if it isn't fully interactive that shouldn't be a big problem.

STUD-1754

STUD-1306