Read through Macros. Added functions to converter.

I had broken the markdown converter on previous commits.  I added these
functions to fix it:  textbackslash, textless, textgreater, ldots,
textsuperscript, textit, textbf.  I also added a literal dollar sign and
support for the ToDoNotes commands.

Use tab for indentation in the convert Haxe files.  But a mix is used in
Haxedoc.tex.  Is there a strong preference either way?