generate-packages-sources

some more changes:
 - chdir before we call the generate function
 - dont include architecture all
 - use commands.getstatusoutput
    this breaks the try, finally: block. using os.system() it works nicely,
    but the output is a hell. using commands.getstatusoutput the finally:
    is called to early, removing the config for apt-ftparchive, breaking it.
    ugh, bad.
 - the whole mess with the config inside dbconn.py needs to go, as well
   as the special cases for the tree configs. should be an aptconf class,
   but thats a task for when this fully works

Signed-off-by: Joerg Jaspert <joerg@debian.org>