Studio: correcting font weight/display issues

* reducing font-weight on component adding menu
* adding in and applying demi-strong font-weight
* adding in $color-copy-emphasized variable
* correcting stateful xblock settings styling nesting
* syncing video player xblock-based controls font-weight

STUD-2109
Re-use GA cookie when sending server-side events to Segment.io
Update bok-choy version
Merge pull request #4904 from edx/talbs/studio-fix-font-weight

Studio: FIX - Font Weights
Merge pull request #4926 from edx/zoldak/update-bok

Update bok-choy version
Merge pull request #4893 from edx/web-analytics/pass-ga-cookie

Re-use GA cookie when sending server-side events to Segment.io
Fix Studio to gracefully handle xblock JavaScript errors

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.