Implemented Pointers to neighbors

Now, neighboring particles have pointers to their neighbors.
So, forEachPair() is only needed for Lennard-Jones, if they are to close.
Therefore, we set the cutoff-radius to pow(2, 1.0 / 6.0), no matter, what
the input file specifies.

Output allows now to write rows and columns, so a membrane can be better
visualized.
Created files to allow profile guided optimization
Merge branch 'master' of https://github.com/the-wolf/PSE-Moleculardynamics