Provide a Python script to create new source files
So far the only option provided is to use XCode templates, but they aren't used by Jérôme (who is using VSCode) or I - we most often just copy existing files and modify the content.
It would be better to provide a more generic way to write new files and limit boilerplate; most of what we actually need is in fact already present in other Python scripts (especially since #1899).