26902 Initial code review

Created a branch from the very first commit to be able to review the whole code written so far.
This does not mean that a merge should be done after the review is done, this is a "dummy" pull request.
Loggers are usually not used like that : logger.debug is always called, and the debug message is issued or not by the logger, depending on its level. So it would be better to define the logging level around line 117 with the engine "debug_logging" setting and get rid of the test here. For example, that would allow to have different handlers, one logging systematically everything into a log file ( including debug ) and another one just displaying "info" in the UI.