Init xmp py script

Python scripts (Eric4 project)
that conditionally (re-)generate LilyPond scores.

Can collect
- all scores referenced from a LaTeX document
- all score in a given file tree

Can compile them
- all (new project/change of layout files etc.)
- if pdf is missing
- if source has been updated

Depending on the type of the music example (given as a variable inside the document)
- renames pdf (e.g. removing the .preview substring)
- removes unnecessary files (.eps, .png)
(- writes latex code for inclusion)

This commit inits an empty project
musicexamples: Move py folder

musicexamples is now a separate subdir (-project).
Its Python project should have its own subdir below musicexamples