Set CJK document language instead of adding a note.

Set CJK document language instead of adding a note.

Instead of annoying the user with an automatically created note in the output
document which she needs to delete manually, determine the document language
automatically for documents that use CJK. This is done using a heuristic which
roughly counts the number of characters in each language and sets the one that
is used most often. This is not perfect, but it works for the two major use
cases: A document with only some CJK parts (in this case the babel language is
used), and a document which is mainly written in one CJK language. It is only
a minor problem if the heuristic is wrong, since the TeX export is still
correct, and there is no spell checking support for CJK anyway.
Now all regression tests do pass except for some relative path issues
depending on the location of the build directory.