changes to address issues with new xcode changes

[theoneineed]

changes made:

1. getppm file had a typo (in pm.sampling.paradram) --> prevents the breaking down post the completion of sampling
2. cmakelist in xrc folder (enforced c++ language compilation) to circumvent the xcode bug issue
3. new pm_sampling.cpp file (pm_paralellism already existed)
4. subPlot.m file needed the notes meant for doxygen to be properly commented for it to be properly defined as a class --> reading functions run now and the visualization is properly running

[shahmoradi]

Thanks Nabin. I address part of your pull request (getppm) in a separate pull: Update getppm.m #55
For the C++ mex file, it appears to be 35 times slower than the original C file.
Let's identify the cause of slow down, fix it, ensure its cross-platform portability and make another pull request.