31.2 resubmission, highlighting implementation,..

A new stylesheet has been added to accomodate styles for VBA syntax
highlighting. I will likely create a common syntax stylesheet at some
point too. I developed the PHP class to handle highlighting as well, but
it is mostly inactive at the moment as its output is being interpreted
literally by parsedown (e.g., <span> to &lt;span&gt;).

One image was renamed for 31.1, and the markdown document changed
accordingly.

Some other assignments have been updated, which consists mainly of small
changes. The 42.3 Technical Documentation is included in this.