python-six: Removal of python2 & 3 addon versions of six

python-six: Removal of python2 & 3 addon versions of six

- six is a python compatibility module to enable modules to run on
   both python2 and python3. The code from six has to be copied into
   any other module/project that is intending to use it.
- With the planned removal of python2 then neither version of this
   compatibility module is needed.
- Removal of the lfs and rootfiles. Although python-six is an addon
   its rootfile was installed into the common folder rather than the
   packages folder.
- Removal of the python-six and python3-six entries in make.sh

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Reviewed-by: Peter Müller <peter.mueller@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>