Additional API methods for Dropdown

[VizuaaLOG]

Over the next few versions I think it would great to expand the API methods available, allowing certain settings to be changed at run time, rather than needing to recreate the component. The below are ideas for the dropdown popup, any other ideas please just comment!

• close() - Closes the dropdown
• open() - Opens the dropdown
• toggle() - Toggles the visibility of the dropdown
• isVisible(): boolean - Returns true if the dropdown is visible, false otherwise
• trigger(event_name: string) - This will trigger the provided event on the dropdown instance. Note: This wouldn't be restricted to documented events, so could be used for handling custom events