added new rendering mode with particles.

* Change MPI_Reduce -> MPI_Allreduce so that if not all rank post it, renderer freezes
* Added new rendering mode with particles. The appropariate parms.txt files is in paramsNew.txt. To enter new rendering mode press 'p' after the renderer starts

*Know issues:  problems with parameters read from the params file if new volumetric rendering mode is default.