Spike - investigate impact of upgrading to Bootstrap 4.x

[TaniaSchlatter]

Bootstrap is currently on release 4.2.1. As we look at UI changes to the dataset and file page, it makes sense to consider migrating, and get a sense of impact.

[djbrooke]

Closing out this spike for now, as the answer is "extremely high" -

#4219 (comment)

@TaniaSchlatter and @scolapasta - you and I should work together to determine the appropriate time and method to introduce such a large change to the application.