Fix rrule for * and add support for constant operations #211
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I am a bit unsure what to do here. I think we should define
rrulebased onLinearAlgebra.dotso we should remove the definition of the rule fordifferentiateand keep the old one for*.@harris-mit I would expect that the current rule for differentitation gives incorrect result when you use it with AD since it assumes a scalar product that is not what is used, does it work for you ?