This commit fix most issues introduced by the new widget system. It
is not production ready and will require multiple commits to fix
individual issues.
The new widget system is better suited for modules like Radical than
the previous one. Over time, this breakage will probably end up being
a good thing. However, for now, expect multiple errors.
The changes:
* The draw "wibox" argument is now a "context". "context.wibox" is
the equivalent. This will allow passing the Radical structure to
the draw method without storing it in the widgets.
* "fit" now have a new required "context" argument for the DPI, this
will allow removing the "default_height" variable Radical is using
to scale the UI on HIDPI systems. This will allow size policies to
be passed to the fit method
* "draw" has been splitted into "draw", "draw_before_children",
"draw_after_children" and "layout". This simplify the overlay
system and will allow cleaner code
* Drawing outside of the widget clip is no longer supported, this
break multiple Radical item.style. This will allow better
performance and less redraw once the new system issues have been
fixed