added foundation option flat

fsl_mrs_mce/mc_in.py

@@ -55,6 +55,7 @@ def conc_df_from_file(input_path="input/", foundation="vivo_average"):
                 "basis/fit_conc_result.csv").mean().to_frame().transpose()
         except:
             print("No basis/fit_conc_result.csv file supplied")
+    # Sets all initial molecules, including some groups, to 0
     if foundation == "flat":
         try:
             df_foundation = pd.read_csv(