Denote combinations of units with forward slash instead of dashes.

[MattDornback]

Using dashes for combinations of units (i.e. Cobble-Boulder) to denote co-occuring elements creates confusion since there are hypenated units in CMECS (i.e. Silt-Clay). Combining the hyphenated unit with the co-occuring units would be indecernable (i.e. Cobble-Boulder-Silt-Clay). Instead, co-occuring units should use a forward slash to not conflict with the hypenated units (i.e. Cobble/Boulder/Silt-Clay).