Improvements to handling of amount/conc for species

Number successful:          642 out of 870 (73.793106 %)
  Number completed:           767
  Number failed (mismatch):   125
  Number failed (exception):  103
  Number unsupported:         155
  Number skipped:             107
  Number not found:           48

  Range:                      1 -> 1180

  Number LEMS points:         30000
  Tolerance:                  0.01