Many doc improvements for Preflow (#176)

- More precise doc for members.
- Add doc for public types.
- Hide the doc of the traits class parameter.
- Removing \author comments.
- Use \tparam for template parameters.

 if WANT_TOOLS

 bin_PROGRAMS +=

 dist_bin_SCRIPTS += tools/lemon-0.x-to-1.x.sh

 endif WANT_TOOLS