Add compute_mole_sources, etc. to KineticsEvaluator

May be nice to be able to get the net production in mole units instead of mass. This pull request adds the functionality for that; old API is still there. Mass versions now internally call the mole version then scale at the end. Make check worked for me on my workstation and laptop. Want to use this right away on the stirred reactor stuff, so I'll merge myself. Throw a bug report at me if this breaks y'all.