Summary:
* adds a smoke test to grist-core
* fixes a problem with highlight.js failing to load correctly
* skips survey for default user
* freshens docker build
Utility files in test/nbrowser are moved to core/test/nbrowser, so that gristUtils are available there. This increased the apparent size of the diff as "./" import paths needed replacing with "test/nbrowser/" paths. The utility files are untouched, except for the code to start a server - it now has a small grist-core specific conditional in it.
Test Plan: adds test
Reviewers: dsagal
Reviewed By: dsagal
Differential Revision: https://phab.getgrist.com/D2768
