Delaunay: Set tolerance in a more transparent way.
EnrichmentItem: improved calculation of tangential level set function in
computeIntersectionPoints().
XFEM: 
 *Now use factory pattern to construct EnrichmentFront. 
 *Modified computation of normal signed distance in beyond the crack
tips. 
 *TrPlaneStress2dXFEM now uses the default element subdivision routines.
Missed one file in previous commit.
UserDefDirichletBC: 
 *Pass an array of node coordinates instead of passing (x,y,z)
separately.
 *Pass dof->giveDofID() instead of dof->giveNumber().