remove matrix_class_string as it is redundant, closes #95
remove matrix_class_string as it is redundant, closes #95

Spandex-at-Exeter/demography_database,Spandex-at-Exeter/demography_database,Spandex-at-Exeter/demography_database,Spandex-at-Exeter/demography_database,Spandex-at-Exeter/demography_database