Pass DDT subfields into Group Caps.

[dustinswales]

Description

If you try to pass a sub variable of a DDT directly into a scheme, the array reference in the Group call string will be incomplete.

For example, using the testing introduced in #637, if you pass the components of the ty_rad_sw DDT into the rad_sw scheme, the full array reference will be incomplete.

Snippet from test_host_ccpp_cap.F90:
sfc_up_sw=phys_state%sfc_up_sw(col_start:col_end)

The complete call string should be:
sfc_up_sw=phys_state%fluxSW%sfc_up_sw(col_start:col_end)