Are all the indexing types thread safe?

[mnlevy1981]

I noticed that the surface forcing output indices (sfo_ind) is a module variable in marbl_interface_types.F90, which probably isn't thread safe. I think we want all the various indices (surface forcing, surface forcing output, diagnostics, tracer, etc) stored in the marbl_interface_class so that there are copies for each MARBL instance.

[mnlevy1981]

Per #59 there are nine indexing types. Seven are already part of the interface:

1. marbl_tracer_index_type
2. marbl_living_tracer_index_type
3. marbl_surface_forcing_indexing_type
4. marbl_surface_saved_state_indexing_type
5. marbl_interior_forcing_indexing_type
6. marbl_interior_saved_state_indexing_type
7. marbl_surface_forcing_output_indexing_type

But two are module variables in marbl_diagnostics_mod.F90:

1. marbl_surface_forcing_diagnostics_indexing_type
2. marbl_interior_diagnostics_indexing_type