Remove failed implementations.
Remove _ from widget description fields.

Widget's description should be public.
Merge branch 'master' into gmm
Refactor toolbar.

Initialize modes in lazy property, store selected mode in Setting.
Refactor toolbar.

ToolbarButton class for button definition, better handling of widget
toolbars.
Refactor Parallel Coordinates widget.

underscored fields, refactored construction of settings panel
camelCase to underscore
Update.
Refactor toolbar.

Initialize modes in lazy property, store selected mode in Setting.
Refactor toolbar.

ToolbarButton class for button definition, better handling of widget
toolbars.
Refactor Parallel Coordinates widget.

underscored fields, refactored construction of settings panel
camelCase to underscore
Refactor OWVisWidget.
Fixed a bug introduced in 4b803479.
Do not try to match non context settings.
Refactor OWVisWidget.

- Replace callbacks with method attributes_changed, which is called
whenever shown attributes or hidden attributes change.
- shown_attributes and hidden_attributes are now private, as they
  contain tuples needed for list items. Attribute names can be accessed
  using properties with the same names. Setter for shown_attributes
  replaces setShownAttributeList method.
Cleanup
Fixed a bug in show/hide attribute.
Code style.
Refactoring.

camelCase, fixed a few bugs when modification buttons would not update
properly in some cases.