ComponentGroups and refactored Interaction

Major changes:

• Interactions are refactored, much simpler API now, more work is done by the consumer when crafting a callback rather than by the base interaction logic. This allows them to be more general and flexibly handle special cases.
• ComponentGroups now allow multiple components (eg multiple renderers, or a renderer and hypothetical legend) to be overlaped
• xAlign and yAlign are handled more elegantly in the component class, and now have setter methods