Added first version of simple water

This is for #90 and based on https://github.com/iea-annex60/modelica-annex60/blob/446aa83720884052476ad6d6d4f90a6a29bb8ec9/Annex60/Media/Water.mo
Corrected cp

This is for #90 and applies c9cb844f1f81ef9cd635e065e71d5eb5c1d7a552
First implementation of water for #90
First implementation of water for #90