Add control event handlers for enabled and visible state change

[James Croft]

Is your feature request related to a problem? Please describe.
At the moment, there is no way to know if the enabled or visible state of a view has changed with the current implementations of Control and Page across all platforms.

Describe the solution you'd like
There should be event handlers associated with the properties.

[James Croft]

Thanks for the review @tom-made! Merge in and closing this off.