HTML Widgets; New widget.UI.VisualiseControlChanged method added to show a visual cue when a control has automatically been updated

A new widget.UI.VisualiseControlChanged method has been added.

This is currently used in the Account Disbursement wizard HTML Widget when changing any controls caused the "Due Date" to be calculated and updated to a different value automatically.

NOTE: Currently this method has only been used on the widget.UI.DateBox control and this is the only control it is currently guaranteed to work correctly with.