createBH Creates a boundary topology USAGE: [BH, BMother] = createBH(H, HN); [BH, BMother] = createBH(H, createHN(H)); DESCRIPTION: Given topology H and its neighbourhood HN, will create boundary topology BH. Can also produce BMother which defines index into H to which boundary element belongs to. INPUT: H - Topology matrix HN - Neighborhood topology matrix OUTPUT: BH - Boundary topology matrix BMother - Vector in which each row defines an index in H to which the boundary element belongs to This function is provided with ValoMC