add list of file_model_csv and file_model_csv_w_path
delete xls file
Revert "delete xls file"

This reverts commit d5989cbb6ad2089f6c5e7dc420c4385461351d6d.
Move data collection from csv into a function

Data needed for plotting is collected from csv file and returned to
plotting routine.  This will allow a loop to be generated for adding
gray-scale shading.