More testing: Frescobaldi Source export options

[Urs Liska]

I have another request for testing some new features in Frescobaldi:
improved options for copying/exporting colored source code. These are
useful for pasting LilyPond code in HTML pages like blog posts or other
things like e.g. http://book.openlilylib.org/cg/coding.html. The
function to automatically highlight code examples upon the generation of
the book actually was the trigger to finally look into this issue.

If you run Frescobaldi and python-ly from their git repositories I'd be
happy if you could test the functions. Please make sure you have the
latest commit from both repositories as the Frescobaldi code relies on
newly merged code in python-ly. checkout the 'source-export-options'
branch and go to "Edit->Preferences->Editor Preferences->Source export
preferences.

My questions are:
- Is there anything strange or wrong with the options (the interface)?
- Can they be understood (with the assistance of the user guide)?
- Is it possible to select combinations that produce meaningless
  or even wrong results?
- Does output work in all cases?
- There are two options with dropdown boxes. Are there any options
  missing here or should these even be made editable?

Thanks in advance
Urs