2-d Refinement based on Haar Pyramid
fine = HRefine2d(coarse,L)
2-d image at a coarse scale: length(coarse)=n
integer >=1. number of generations to refine by
2-d image at a fine scale: size(fine) = 2^L * size(coarse)
Trivial Refinement scheme is used to refine boxcar averages on a grid of n*n points, imputing averages on a finer grid of 2^L n * 2^L n points. Specifically, for L generations, each block in the parent is replaced by a 2*2 block in the child, all having the same value as in the parent.