Added ability to color molecules

Deprecating the add the method used to register molecules before and replaced with one that requires RGB color values to color the molecules.
The deprecated method when called will supply the newer method with random RGB color values.
Currently colored molecules:
Water ( As originally requested by @MFernflower )
Cellulose
Carbon Dioxide
Nitrogen Dioxide
Toluene
Potassium Nitrate
Trinitrotoluene

Comment below if you wish that I color more molecules.