refactor python packaging, added python3.9

CHANGELOG.md

CMakeIncludes/prepare_version_tag.cmake

CMakeLists.txt

deploy/build_env/centos/build.sh

deploy/build_env/centos/install_curl.sh

deploy/build_env/debians/build.sh

deploy/build_env/debians/install_curl.sh

deploy/build_env/manylinux2010/Dockerfile

deploy/build_env/manylinux2010/build.sh

deploy/build_env/manylinux2010/build_image.sh

deploy/build_env/manylinux2010/install_curl.sh

docs/site/examples/install_python_clients_pip.sh

docs/site/examples/install_python_clients_pkg.sh

docs/site/freeze_version.sh