integrate USER-MOP package into build and documentat system. apply latest LAMMPS programming style conventions

liblammps.pc: add lammps version

cmake: add FindLAMMPS.cmake.in

Silence  USER-CGSD warnings

Fixes various compilation issues

Bond/react: treatment of simultaneous competing reactions

added manpage from debian package

Added Axilrod-Teller manybody potential

cmake: fix install of potential files

cmake: sort package in header

Fix compile warnings when building with pedantic flags

Add an '/' at the end avoids the double potentials/ subdir.

rebase