[IMP-dev] benchmarks

After the discussion of connectivityrestraint performance, I suggest we add a benchmarks folder to IMP. This folder will have C++ programs which time some aspect of IMP so that we can see how speed is doing (I can't figure out how to profile code run from python, which is necessary any time we want to get into running times). Eventually it would be nice to have them run periodically on a reference machine and recorded, but that can wait as it sounds annoying to set up :-)