Implement salinity and volumetric salinity #210
Description
Salinity can be measured as mass of salt per volume of water or in mass of salt per mass of water:
- PhQ::Salinity (dimensionless; mass of salt per mass of water)
- PhQ::Unit::VolumetricSalinity (mass of salt per volume of water)
- PhQ::VolumetricSalinity (dimensional; mass of salt per volume of water)