_NAME_
get_instrument_id_from_struct_name

_PROTOTYPE_
id = get_instrument_id_from_struct_name(structName)

_SHORT-DESCRIPTION_
Get the data type's instrument ID ('c' for CRIS, 's' for SIS)

_DESCRIPTION_
Get an ID for the instrument associated with the data type
given by structName.

_INPUT_
* structName is the name of the data type of interest.

_OUTPUT_
* Either 'c' for CRIS or 's' for SIS.