Fix "Add document" modal

Wasn't being sized properly; wysihtml5 stylesheet was missing.
Various fixes for adding documents inline

Styling of zotero data; toggling between first/last names or literal
name; dumb bugs.
Start changing code about note section ordering

Remove code about a `section_ordering` attribute of notes as a whole,
beginning to replace that with `ordering` attribute of individual
sections.
Handle section ordering; refactor section editing

Ordering is now handled within the `add` and `save` methods of
collections of note sections. This means just using `at` and `save` like
normal will work.

This might be a bummer of a way to do things but ordering is hard.