add more thorough checks on parsing reaxff force field and signal when the lgvdw setting is correct.

Allow limiting of the maximum energy change of an atom in
fix dt/reset in addition to the existing distance limit.
Useful especially for high-energy irradiation.

Added pair styles lj/expand/coul/long to USER-MISC and its gpu version to GPU package, added lj/cut/dipole/long/gpu; and added an example Makfile to build GPU package for multi-arch

this will trim warnings and error messages when compiling using the CMake
build system, which uses full paths. as a bonus,one can now see, if a
source is taken from a package or not.