Add customizable title for Doxygen reference page in nt2.doc

nt2_doc_doxygen can now be called with a second parameter that
is used as the title of the corresponding reference section in
the final output.
Add an extensible file to list Doxygen predefs

Some Boost macro and constructs add unecessary noise to our doxygen
output. This patch add an easy to extend files listing common macro
and construct to remove.