Implement the remaining modes of reasoning in nsolve, and thus
enable configurable puzzle difficulty. I'm only generating grids up
to Times level (complicated non-recursive analysis but guessing
never required); I wouldn't object to providing a Telegraph
difficulty level (guessing required) but it turns out to be very
hard indeed to generate at random. I might still add it later
(probably under the name `Unreasonable' :-) if I can think of an
efficient way to find them.
git-svn-id: svn://svn.tartarus.org/sgt/puzzles@5682
cda61777-01e9-0310-a592-
d414129be87e