fix compile issue
Refactored OneBody to use particleIndices vector

Previously it was using 3 integers instead of a vector
Setup support for NonBondedMethod and box dimensions
implemented PBC for one body
Added test on 50 molecules
Updated python wrapper for refactored OneBody force
Python support for PBC
Merge pull request #3 from zonca/all_pbc_pbc_onebody

All pbc pbc onebody