local virial implementation of PME electrostatics

v5.0-virial-1.1

long range correction to pme virial fixed

v5.0-virial: local pressure calculation added.

Notes:
1) computes the pressure contribution per particle,
   adding a vir[] term to the .trr file whenever
   force dumping is requested. Even though it is
   called "vir" it is actually the pressure tensor
   diagonal components times the volume, in bar * nm^3.
   The kinetic part is included.
2) energy should be calculated with the same
   frequency as force to get the pressure contribution.
3) PME is not working, only pure Ewald is, but this is slow.
   Use mdrun's rerun option to compute the pressure from a
   previous trajectory where PME has been employed.
4) Only shake constraints is implemented. Water topologies
   should be changed to avoid using settle
5) The zero-th timestep lacks constraints contribution
6) Other bonded forces are not included yet

v5.0-gaussian: Gaussian charge distributions

C + SSE4.1 kernels implemenation of PME electrostatics
for Gaussian charge distributions (coulombtype = PME-G)
Adds the Gaussian width as a new property for the [ atoms ] entries