`TextBoxOverlay` incorrectly overrides `Component.padding`

[corranwebster]

Problem Description

The base Component class has a padding trait which is a Property that can take a number of different values, but TextBoxOverlay which is a subclass of Component, overrides this as an Int.

This is used as a margin around all sides of the text inside the component's rectangle, rather than the padding outside the rectangle.

A simple fix would be to re-name the trait on TextBoxOverlay to something else (eg. text_padding or margin).