Update package format to reduce warnings

1. Move from `python_support` to `dh_python2` as described at https://wiki.debian.org/Python/TransitionToDHPython2?action=show&redirect=Python%2FPythonSupportToDHPython2

2. Update package format to `3.0 (quilt)`

3. Update to debhelper/compat to `9`

4. Generate few warnings as possible on package building