* Python: Disable distribution of static library on linux and macos; add environment variable LIBUNICORN_PATH to let user specify location of native library; prevent build of native library if this option is enabled; closes#869
* Python: Update README.TXT to describe how to manage the building and usage of the native library
clarify in which directory to build the core project and install the python bindings. when i went to install the python bindings, i was momentarily confused why the root Makefile didn't have an `install3` target.