WIP: Add skeleton for MQTT extension based on part of OPC-UA extension.
For now generated code makes no sense but persistently-configurable-C-generating-extension infrastructure is there.
*.pyc
**/__pycache__
.vscode
**/build/**
*.class
**/.svghmithumbs/**
**/my_*.der
**/my_*.pem
tests/tools/Docker/requirements.txt
**/management.json
**/.secret
doc/_build/**
doc/locale/**
C_runtime/**/*.d
C_runtime/**/*.o