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.
The code is now more event-driven when it comes to rendering notices
and their related HTML elements, since we can't have direct calls from
core to a plugin.
lib/activitymover.php has a function to move a Favorite activity which
will not happen now. The move must be pluginified and performed as an
event which plugins can catch on to.
Now we have to fix any code in the core which directly uses the Fave class
or any other favorite stuff, since it is pluginised and thus might not be
available on some installations.
