enable multi-processor NEB replicas

doc/src/Manual.txt

doc/src/neb.txt

examples/neb/README

examples/neb/in.neb.hop1

examples/neb/in.neb.hop2

examples/neb/in.neb.sivac

examples/neb/initial.hop1

examples/neb/initial.hop2

examples/neb/initial.sivac

examples/neb/log.28Sep16.neb.hop1.g++.4

examples/neb/log.28Sep16.neb.hop1.g++.8

examples/neb/log.28Sep16.neb.hop2.g++.4

examples/neb/log.28Sep16.neb.hop2.g++.8

examples/neb/log.28Sep16.neb.sivac.g++.3

examples/neb/log.28Sep16.neb.sivac.g++.6

examples/neb/log.28Sep16.neb.sivac.g++.9

examples/snap/Ta06A_pot.snap

src/REPLICA/fix_neb.cpp

src/REPLICA/fix_neb.h

src/REPLICA/neb.cpp