feat(theming config): Added config for this-modifiers and themed-style

This allows developers to configure at a project-wide level whether or not to
render the inverse-this and secondary-this modifiers for styles that use them,
as well as whether or not to render the fully qualified themed-styles along with
the cascading versions - e.g. .blue-inverse-secondary-button rather than
.blue.inverse.secondary.button being the only way of achieving that style.