Removed unused variable.
Increased max number of distinct elements for Brenner-type potentials to 3.
Removed unused variable.
Added implementation of the Juslin W-C-H potential (JAP, 98, 123520) that needs three body parameters in the computation of the bond-order.
Added Juslin W-C-H parameter set (JAP, 98, 123520).
Added bulk properties test for Juslin W-C-H potential.