New object: NcWLSurfaceMassDensity
This object is implements various functions related to lensing cosmology, namely, the surface mass density $\Sigma (R)$, its mean $\overline{\Sigma}(<R)$ and excess $\Delta\Sigma (R)$, the convergence $\kappa (R)$, the shear $\gamma (R)$ and reduced shear $g(R)$.