Changing KDEKernel into a Base class for creating kernel function objects
Adding skeleton of the PolynomialKernel class
Adding support for 2nd-order uniform and epanechnikov kernels.
Adding support for biweight, triweight and general s-case polynomial kernels.
Adding support for higher-order symmetric kernel functions
Adding new Quadrature class to compute definite integrals
Adding n=5 quadrature support and ability to change quadrature set
Adding MomentFunction to KDEKernel and removing evaluate(double, Boundary)
Adding the boundary kernel as an option for boundary correction method
Adding unit tests for the refactored KDEKernel class hierarchy