Mkdocs-theme-bootstrap4

* Make dependency upgrades a little easier
* Add blockquote styling
* Add table styling

* Bump Bootstrap to 4.4
* Fix navigation expand/collapse on mobile
* Correctly detect Yarn on Windows systems
* Document build dependencies
* Untangle `develop` and `sdist` commands

* Vendor all of the dependencies for easier offline development
* Clean up some of the templates
* Remove all non-essential CSS/JS
* Remove Google Analytics support
* Remove GitHub-specific contributor and publishing metadata
* Add the missing 404 template
* Remove leftover Bootstrap remnants
* Fix nested navigation