Add ability to set ALTERNATIVE_REFPROP_PATH and read environment variables
Add ability to set ALTERNATIVE_REFPROP_PATH and read environment variables

The environment variable COOLPROP_REFPROP_PATH can be set to indicate to CoolProp what path should be used

Closes #1235

DANA-Laboratory/CoolProp,dcprojects/CoolProp,JonWel/CoolProp,DANA-Laboratory/CoolProp,henningjp/CoolProp,JonWel/CoolProp,henningjp/CoolProp,henningjp/CoolProp,henningjp/CoolProp,JonWel/CoolProp,DANA-Laboratory/CoolProp,CoolProp/CoolProp,JonWel/CoolProp,henningjp/CoolProp,DANA-Laboratory/CoolProp,dcprojects/CoolProp,JonWel/CoolProp,CoolProp/CoolProp,dcprojects/CoolProp,CoolProp/CoolProp,DANA-Laboratory/CoolProp,DANA-Laboratory/CoolProp,CoolProp/CoolProp,CoolProp/CoolProp,henningjp/CoolProp,CoolProp/CoolProp,CoolProp/CoolProp,henningjp/CoolProp,dcprojects/CoolProp,dcprojects/CoolProp,DANA-Laboratory/CoolProp,dcprojects/CoolProp,JonWel/CoolProp,JonWel/CoolProp,CoolProp/CoolProp,henningjp/CoolProp,dcprojects/CoolProp