Calling serverError with a clientError status code (4xx) means it will
automatically default to Internal Server Error (500) which is in the
server error status code range (5xx). That is undesirable.

Qvitter had implemented this as a "PublicAndExternal" stream, but
I figured we might as well put it into the GNU social core.

Action now has 'isAction' which compares the loaded Action with names
of classes in an array (added without the 'Action') to its own type.

Since these functions exit (or throw exception) after running, there
is no need to have a 'return' statement or similar afterwards.

commit fb1dfa9e98ded23fb5bdebae6465424a8cb8acd6
Author: Evan Prodromou <evan@status.net>
Date:   Thu Oct 20 10:40:07 2011 -0400

    Use popular notice stream for favorited page

commit e1d409ff738e39061ad35589d546ce9bed456975
Author: Evan Prodromou <evan@status.net>
Date:   Thu Oct 20 10:32:23 2011 -0400

    Use a caching stream for popular notice section

    Instead of a big cached query, we now use a caching notice stream for
    the popular notice section. It uses a single-table query at the
    bottom, then scopes the notices and filters for silenced users. This
    should be much nicer to our database servers.

    Also clears the popular cache when someone favors or disfavors
    something. A nice optimization would be to save the last weights and
    re-calculate them at invalidation time, adding the new notice (or not)
    depending on its own score. That will have to wait for another day,
    though.

commit e9b7ab4c26c95e755adaff53c3957dcfca31c16b
Author: Evan Prodromou <evan@status.net>
Date:   Thu Oct 20 10:31:14 2011 -0400

    Let CachingNoticeStream users skip the ';last' optimization

Revert "Paging fix for public timeline: drop replies from the stuff we pull in for the threaded web view."

This reverts commit 880661de.

* remove superfluous whitespace.
* minor updates to L10n/i18n.

* use correct punctuation
* single quotes when replace was possible
* wording updated when needed

* use correct punctuation
* single quotes when replace was possible
* wording updated when needed

Anil Dash suggested that all implementers of the Twitter API include
support for the remedial RSD format. This commit adds an RSD action
that returns the API root and additional API data to help client
developers discover and use our Twitter-compatible API.

http://dashes.com/anil/2009/12/the-twitter-api-is-finished.html
http://tales.phrasewise.com/rfc/rsd