Abhijit

1. Add PolynomialNonResonantLineShape and SpecialFlatteLineShape (as done in Pentaquark analysis: p0 in Blatt-Wieskopff is taken from the dominant channel and the couplings b/w two channels is the same varying only in phase space factors).
2. Fix RectangularGridSample method of DalitzPhaseSpace class, when sampling from sqDP (included reference to convDP_from_sqDP which had changed to FromSquareDalitzPlot)
3. Add method CalculateIntfFractions (strangely did not exist in the master branch).