suzerain: add dN.x() == 1 case to points

It's nice, when there's only a single collocation point, for it
to be independent of the domain size.  Move that into grid.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@44507 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: save common collocation-point defn

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@44508 0bd85f0b-c151-43b9-a1e9-27231104551f