apply document level marking for simple cases

[jonathanbaker]

as an interim solution can we make a simplifying assumption and hard code marking structures that are intended to apply to the full document?

For example, when the STIX header has a marking structure with handling that uses '//node()' to identify the controlled structure we could mark the whole document as amber without having fully implemented all possible marking capabilities. This simple example tends to align with most of the data we see today.

We would also need to figure out how to display a TLP marking in the html.

[mattcoarr]

This was addressed in beta4.

More extensive support for marking data has a placeholder issue in #42.