new SNAP potential for W

doc/src/compute_rdf.txt

examples/snap/He_He_JW2013.table

examples/snap/W.SNAP_HePair.pot

examples/snap/W_2940_2017_2.pot.snap

examples/snap/W_2940_2017_2.snapcoeff

examples/snap/W_2940_2017_2.snapparam

examples/snap/W_He_JW2013.table

examples/snap/in.snap.Ta06A

examples/snap/in.snap.W.2940

examples/snap/in.snap.hybrid.WSNAP.HePair

examples/snap/log.21Feb17.snap.W.2940.g++.1

examples/snap/log.21Feb17.snap.W.2940.g++.4

examples/snap/log.21Feb17.snap.hybrid.WSNAP.HePair.g++.1

examples/snap/log.21Feb17.snap.hybrid.WSNAP.HePair.g++.4

examples/snap/log.5Oct16.snap.Ta06A.g++.1

examples/snap/log.5Oct16.snap.Ta06A.g++.4

potentials/He_He_JW2013.table

potentials/W.SNAP_HePair.pot

potentials/W_2940_2017_2.pot.snap

potentials/W_2940_2017_2.snapcoeff