largo: NULL workspace on unknown model + test

Also includes NOP deallocation on NULL workspace,
testing in suzerain apps/perfect and suzerain apps/reacting.

Fixes problem from #1536 update 13 where "bl_spatial" was segfaulting.
This is because there's no "bl_spatial" implementation in Largo.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42342 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: improve largo_allocate logging

Dumps out precisely the arguments passed to largo_allocate

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42343 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: mark bl_spatial as unimplemented.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42344 0bd85f0b-c151-43b9-a1e9-27231104551f