OZP-71 - Get the Eventing API code into the new repository.

adding initial eventing api
OZP-73: OZP-13: OZP-297:  Changes needed to be made to fix the tests  & validation
OZP-56: Migrate accordion layouts.

1. Added accordion dashboard and javascript tests.
2. Fixed bug where PanelPanes (in Accordion and Portal) could be dragged from anywhere in the widget.
3. Fixed bug where PortalPane wouldn't render collapsed widgets as collapsed and added a javascript test for it.
4. Fixed bug where PanelPane widgets couldn't be interacted with due to being rendered behind the widget body.
OZP-244 Use Groovy delegates for common functionality