This updates the minimal supported version of CMake to 3.16, which in turn enables us to use more CMake features and have a cleaner build system.
This is the version that provides most new features and also the one we use in our latest docker image for CI.
- Base class with separated event handlers for each Mqtt client event.
- Topic matcher added to support data events.
- Filter class to allow only mqtt valid topic filters.
- Initial code for unit test on the host.
