Specific Energy is incorrectly defined

[hunterpayne]

Specific Energy is energy per unit mass of a chemical reaction. Its unit of measure is J/kg. This is not the same thing as a Gray which also a J/kg but of ionizing radiation only. Units of measure for Specific energy include: Joules/kilogram, kilocalorie per gram (Cal/g or kcal/g), watt hours per kilogram in the field of batteries, and the Imperial unit BTU per pound (BTU/lb). Gray is a measure of absorbed dose (which is different from squants.radio.Dose which is effective, committed or equivalent dose). Also, the comment in Dose.scala needs to be updated to reflect this.