Improvements to SimDictionary for when you have a large number of object...

...s in the game.  Under light load (i.e. under 5000 objects) this code actually runs slower that the stock simdictionary.  When you exceed 5000 objects, the template class actually runs faster and more consistently.
Please wrap this in `#ifndef USE_CLASSIC_SIMDICTIONARY`, or it will break on non-C++11 compilers.