This adds the upgrade to Bootstrap 4, and some basic changes and
some CSS tweaks we needed to keep out UI consistent.
The simpler changes are things like:
* Classes that were renamed
* Adding classes that are now needed (dropdown-item, etc)
* Change an item from a button to a span
* Changing order of items (modal header close button, etc)
* CSS class syntax changes
The other changes are lots of CSS padding, margin, font and
other spacing tweaks.