Merge branch 'py3' into 'master'

.gitlab-ci.yml

indra/cmake/BuildPackagesInfo.cmake

indra/cmake/LLTestCommand.cmake

indra/cmake/Python.cmake

indra/cmake/TemplateCheck.cmake

indra/cmake/run_build_test.py

indra/copy_win_scripts/start-client.py

indra/deps/CMakeLists.txt

indra/fix-incredibuild.py

indra/lib/python/indra/ipc/llmessage.py

indra/lib/python/indra/ipc/tokenstream.py

indra/lib/python/indra/util/llmanifest.py

indra/lib/python/indra/util/test_win32_manifest.py

indra/llcommon/tests/llsdserialize_test.cpp

indra/llcorehttp/CMakeLists.txt

indra/llcorehttp/_httpoprequest.cpp

indra/llcorehttp/httpheaders.cpp

indra/llcorehttp/tests/test_httprequest.hpp

indra/llcorehttp/tests/test_llcorehttp_peer.py

indra/llimage/llimageworker.cpp