Clickable MouseManipulator for this Button.
The default Clickable object provides a list of actions that are called using
one or more activation filters.
To add or remove activation triggers, modify Clickable.activators.
An activation trigger can be any mouse button, pressed any number of times, with any modifier key.
For details, see ManipulatorActivationFilter.
clickable.activators.Add(new ManipulatorActivationFilter(...))
or
clickable.activators.Clear()