SYSML21 — Add standard domain libraries for mathematical and physical constants

There should be a Constants Domain Library that capture all mathematical and CODATA Fundamental Physical Constants as published on https://pml.nist.gov/cuu/Constants/, in particular from the ASCII list of all constants at https://pml.nist.gov/cuu/Constants/Table/allascii.txt. Each constant should include a specification of whether its real number value is exact or not and, if not, what the uncertainty is.