[modules] remove setting widgets via "self.widgets(new list)"

use self.add_widget() for all modules

docs/development/module.rst

@@ -72,7 +72,8 @@ Otherwise, you have a number of ways to handle widgets: - During the
 ``super().init__(...)`` inside the module’s constructor, you can specify
 a **list** of widgets, and those will comprise the widgets (in ordered
 fashion) - During runtime, you can set a new list of widgets by using
-the ``self.widgets(<new list>)`` method of the module
+the ``self.add_widget()`` method of the module to add new widgets and
+``self.clear_widgets()`` method to remove all widgets.
 
 Adding widgets at runtime
 -------------------------

docs/other/NOTES.md

@@ -16,10 +16,8 @@
 ## TODO
 - themes: use colors to improve theme readability
 - convert some stuff to simple attributes to reduce LOCs
-- use add_widget() instead of core.widget.Widget()
 - use widget index for bumblebee-ctl as alternative (??)
 
 # documentation
 Add info about error widget and events for error logging
-- add module contributor doc
 - which location APIs are used?