Constants

This should finish up constants, and achieve parity for constants with Scipy, including their CODATA2010 lookup.

My next procrastination project will be unit parity, I guess. The Scipy units are not done very systematically, it seems. Do you have any preferred template project? Maybe something like `unitConvert( value/DV/DM,  sourceUnit: TemperatureUnit, targetUnit: TemperatureUnit)` or maybe even like `value/DV/DM  kg in lbs` done as `value/DV/DM.kg().in( ).lbs()` ???

Kenta