Refactor updateUnitsMap to use function for updating standard units.
Refactor updateUnitsMap to use function for updating standard units.

MichaelClerx/libcellml,nickerso/libcellml,hsorby/libcellml,MichaelClerx/libcellml,nickerso/libcellml,cellml/libcellml,hsorby/libcellml,nickerso/libcellml,hsorby/libcellml,nickerso/libcellml,cellml/libcellml,hsorby/libcellml,cellml/libcellml,cellml/libcellml,MichaelClerx/libcellml