Add states to the modules and widgets. Widgets are mostly just a
pass-through (backwards compatibility, and ease of use - making states
directly inside the widgets would require more code inside the modules
to ensure that each widget is correctly updated).
Still missing:
- Separators during partial update (right now, it takes one interval
until separators are drawn correctly)
Add a way for themes to specify custom separators. Doing that, make
nicer interfaces for drawing "supplementary" components (separators)
for widgets and generalize the attribute retrieval within the theme.
The core.output module now manages the list of modules and retrieves the
widgets inside draw() itself. That way, details of drawing/updating
widgets are not visible from the outside anymore.
