suzerain: improve constructor, descriptions

Turns out the XXX_definition pattern is to use this sort
of constructor.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42563 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: remove unused using statements

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42564 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: radial_nozzle_definition draft

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42565 0bd85f0b-c151-43b9-a1e9-27231104551f