This allows styling different types of results individually.
It's helpful to visually distinguish different content types.

This PR adds `context` to the javascript result entries
(one of "title", "index", "object", "text") and adds
them as a classes context-title, context-index, context-object,
context-text to the <li> item in the result list.
This allows styling via CSS.

The basic theme only contains the mechanism to add the HTML
classes. It does intentionally not do any styling via CSS.
We reserve that freedom to derived themes.

For the internal sphinx13 theme, I've styled with unicode
symbols, which should give a decent look without the need
to ship our own symbols.

Co-authored-by: Adam Turner <[email protected]>

Co-authored-by: James Addison <[email protected]>

# Conflicts:
#	CHANGES.rst