h: Upgrade or remove Bootstrap dependency

## Feature Request Form
### Problem you are trying to address with this feature

`h` currently uses an out-of-date version of bootstrap on the admin pages. There are a few complexities to simply upgrading the package:

1. There's an odd peer dependency on `popper.js`; `popper.js` dependency also has to be introduced in order to get `4.0.0` to install and work.
2. Even when install "works", it breaks the layout of the admin pages:


(bye-bye menus and layout)

Bootstrap 4.0.0 was only [tagged and released 4 days ago](https://github.com/twbs/bootstrap/releases/tag/v4.0.0) as of writing.

### Your solution

There are three actions one could take here:

1. make Bootstrap 4.0 work with the `h` admin pages;
2. remove or minimize the Bootstrap dependency (i.e. refactor the CSS)
3. do nothing for now

My recommendation for the moment is to take action 3, with an ideal end point of action 2, maybe bundled into some subsequent work on the admin pages as it comes up.