Created common document class

Created a document class that contains all of the code for the basic Black
Box document format and modified the requirements doc to use it. Also
added a custom title-page macro that takes the document title as the
argument.
Added ToC macro to BBDocument class

Added a macro that sets up the table of contents to the BBDocument class,
so it can be called by any document without having to be redefined.
Added macro to change header text

Added a macro to the class file to change the header text to match
the current assignment.