Introduces a mscclpp.get_include() in the Python module. The extension module is now named _mscclpp so that we can have Python code in the mscclpp module. Also does some miscellaneous cleanup.
Co-authored-by: Olli Saarikivi <olsaarik@microsoft.com> Co-authored-by: Changho Hwang <changhohwang@microsoft.com> Co-authored-by: Binyang Li <binyli@microsoft.com>