Replace H tags with divs (modal and preferences form)

This is a very good idea. And there's already similar issues filed to the official GitHub repo:

[Provide configurable consentModal.titleTag and consentNotice.titleTag #425]

But I guess, until this gets fixed upstream, we need to do it ourselves.

To maintain backwards compatibility we ideally also offer a new option in the simple_klaro.settings to configure the consentModal.titleTag and the consentNotice.titleTag.

But first of all we need to find a way to make it work, to get the heading markup-changing JavaScript attached at the right moment and the markup actually changed.

Later we need to get that option in.