Controls no longer need an Addon

- Forms still need an addon for tracking
- Forms set instance on Container
- Containers set instance on Controls when controls are added

In short, when a control is on the screen it is within some container and
that container is within some form.

- Renamed the events to present tense because when they are fired, the
  action is about to be performed, not after.
- Minor structuring

Signed-off-by: Chris Sanders <zidane@outlook.com>