Purpose:returns a unique list of cp names that corresponds to the sel_strings returned by thm_get_unique_sel.pro Keywords: src_idx: an array of source indices sel_str: the sel strings used in sel source selection cp_list: an array of cp's corresponding to those indices Returns: an array of unique cp's structs the correspond to the selected sel_string Notes: --used in thm_cal_fft,thm_cal_fbk --any changes here should probably be mirrored in thm_get_unique_sel.pro