This plugin enables RSSCloud (http://rsscloud.org/) publishing and
subscription handling for RSS 2.0 profile feeds (i.e:
http://SITE/PATH/api/statuses/user_timeline/USERNAME.rss). When the
plugin is enabled, StatusNet acts as both the publisher and hub ('writer' and
'cloud' in RSSCloud parlance), but only for local StatusNet feeds. It's
not possible to use it as a general purpose hub -- for instance you can't
subscribe and get updates to a Wordpress feed from StatusNet using this
plugin.

To use the plugin, add the following to your config.php:

    addPlugin('RSSCloud');

Enabling the plugin will add a <cloud> element to your RSS 2.0 profile feeds
that looks like this:

    <cloud domain="SITE" port="80" path="/main/rsscloud/request_notify"
    registerProcedure="" protocol="http-post"/>

Aggregators may subscribe by sending a proper REST RSSCloud subscription
request (the optional 'domain' parameter with challenge is supported).
Subscribing aggregators will be notified ('pinged') when users they have
subscribed to post new notices. Currently, REST is the only protocol
supported for notifications.

Deamon
------

There's also a daemon for offline processing of queued notices with
RSSCloud destinations, which will start automatically if/when you run
scripts/startdaemons.sh.

Notes
-----

- Again, only RSS 2.0 profile feeds may be subscribed to, and they have
  to be the ones with user names in them, like:
      http://SITE/PATH/api/statuses/user_timeline/USERNAME.rss
- Subscriptions are deleted after three notification failures in a row
  (not sure this is optimal).
- The plugin includes a dummy LoggingAggregator class that can be used
  for end-to-end testing.  You probably don't want to mess with it.

TODO
----

- Figure out why the RSSCloudSubcription can't ->delete() or ->update()
- Support pinging via XML-RPC and SOAP
- Automatically delete subscriptions? Point of reference: Dave's hub
  implementation auto-deletes them after 25 hours. WordPress never deletes them.
- Support additional feed URL addresses for the same feed (e.g.: by numeric ID,
  ?user_id=xxx, etc.)
- Support additional feeds that make sense (e.g: replies)?
- Possibly use "rssCloud" (like Dave) instead of "RSSCloud" everywhere
