documentation of units in KineticsType derived objects

Documentation of units have been updated. I discussed with Sylvain for the units used, but a carefull double check is needed (I restored the original state of the 'deletes').
Also, some units of KineticsType objects (e.g. pre-exponential factor and rate) depends of the order of the rate,  adding a kind of 'order' attribut to KineticsType would provide 'self-descriptive' objects.