Python wrapper for Estimator C++ class #2

I've rearranged the C++ source/build directory layout. The C++ source and header files are now located in `src` and `include` respectively. The C++/python interface code is located in `pysrc`. I renamed the Estimator skeleton class to EstimatorEngine to avoid a name conflict with the python Estimator class. The C++ source files are now built in a subdirectory of their directory called `.obj`.