Allow to Workaround the first-child Issue

When the Content Marker Macro renders an identifier (or by any other means the macro requires to render an additional div element), the contents of the macro will probably be rendered as the first child of this container.

This may cause the application of CSS rules that now apply first-child styles, even if this macro is rendered logically not as a first child.

We add a feature to the macro so that the writer may configure the behavior. The value of a parameter, document property, or space property will control whether or not an additional span element is rendered thus making the content of this macro not its first child.

This feature is considered experimental.