Refactor partials to not use instance variables

If partials were to use instance variables, parents that render these
partials are forced to have instance variables of the same name.

Get get around this constraint, partials should always use local
variables, which will be passed in by parent when calling render.
Give rules#edit UI a container, fix quirks with .docs, add .page-bottom

With a container with border, rules#edit UI looks baron.

.docs had some quirks with word wrapping.

Many pages' bottom-most element is a form, which has a 20px bottom
margin. Other pages have an add button which doesn't have any bottom
margin and doesn't look add. Add to these buttons .page-bottom class,
which gives them a 30px bottom margin.