The converter now maps arbitrary open blocks to LaTeX environments.

See the README, new section 4.3, "LaTeX Environments" for details.
Briefly, a file, "new_environments.tex" is generated which
contains a simple but serviceable definition of a LaTeX
environment corresponding to the given open block.  These
definitions are stored in the file "new_environents.tex"
The user can use this file as a starting point for customized
environments.  Via this mechanism the converter needs to "know"
very little about LaTeX.  

NOTE: I used global variable $latex_environment_names  to accumulate
the block titles encountered by the parser.  There is probably a much
better way, so please feel free to change this.