Getting rid of NoticeListItemAdapter, putting more into ActivityHandlerPlugin
and relying on plugins to handle rendering code of the content. This gives us
a lot more structure and consistency in notice structure and allows activity
plugins to stop rendering certain kinds of notices more easily.
There should also be a property for an ActivityHandlerPlugin class to avoid
rendering notices in the ordinary stream, so we don't have to overload stuff.
Lost dependency of OStatus plugin for lib/microappplugin.php, whoo!
also noting which plugins should be upgraded to new saveActivity support.
Favorite plugin won't work with the new system just yet, it doesn't have
the necessary functions to extract activity objects, but that's coming
in the next (few) commits.
lib/plugin.php now has a parent onAutoload function that finds most common
files that are used in plugins (actions, dataobjects, forms, libs etc.) if
they are put in the standardised directories ('actions', 'classes', 'forms',
'lib' and perhaps some others in the future).
