Scalar solves shouldn't need QuadratureSet

[JessicaRehak]

Current implementations require a QuadratureSetI to calculate spherical harmonic moments, even for a scalar solve (in this case the set only contains a single point of weight 1.0). There should be a class ScalarCalculator : public SphericalHarmonicMoments that just moves the value of the angular solution into the moment. This would not require a quadrature set as a dependency.