Concatinating with settings.STATIC_URL is no longer reccomended for creating
URLs to static resources, because it doesn't take the configured storage engine
into account. For example, a site using S3 to store its static files will need
static URLs that link out to S3, rather than relative URLs within the same
domain.
I replaced it with django.contrib.staticfiles.templatetags.staticfiles.static()
in python example code, and the {% static %} tag in template examples.
Most of the samples were already 4-space indented, but a few were using 2-space,
which is both inconsistent and, when it happened with Python code samples,
incompatible with PEP8.
Since the collections infrastructure itself does not know about the object types that
can exist within collections, this requires a new hook `describe_collection_contents`
to allow collection contents to be discovered.
These were introduced in 9d7d016b7c to support menu item highlighting, but this mechanism was superseded by #1186. There's no sign of any code still using these classnames, and any code that relies on them would be liable to fail on non-English-language sites anyhow (since the menu item name is derived from the label by default, and the label is a translatable string).
