bugfix python3k sync C and python file pointer

- crazy difference between python3 and python2. Operating on a
  duplicated file descriptor on C actual seems to corrupt the
  knowledge of the python file object about it's position.
- this was not a problem on python2 though
py3k: bytes on the outside, Unicode on the inside

- better gse3 porting which uses the "Unicode sandwich: bytes on the
  outside, Unicode on the inside" see
  http://pyvideo.org/video/948/pragmatic-unicode-or-how-do-i-stop-the-pain
- tests test_libgse2.py, test_core.py, test_libgse1.py and test_paz.py are
  now passing on python3 and python2
- and minor refactoring