[CLEANUP] Two interaction related verbs (pvc.Chart#{renderInteractive, r...

...enderResize}) to reduce access to private details and make it easier to do these frequent tasks: re-render due to selection/activity changes and re-render due to size changes.

@pamval please review.
These are 0.001% risk changes, and would be great if they would be included in the forthcoming CTools release.

Two patterns frequently provided in the forums and also for wd's custom dashboards' needs