Removed 3-dimensional arrays from crack module. All functions now accept and return x- and y-positions seperately (i.e. they work 2-dimensinal arrays now).
Removed 3-dimensional arrays from crack module. All functions now accept and return x- and y-positions seperately (i.e. they work 2-dimensinal arrays now).

libAtoms/matscipy,libAtoms/matscipy,libAtoms/matscipy,libAtoms/matscipy