[skeleton] Update Debian packaging template Here are multiple updates to the Debian packaging template provided when running `cubicweb-ctl newcube`: * Switch to source format 3.0 (quilt). * Switch to debhelper 9. * Switch to dh-python. * Switch to Python 3. * Name the binary package `python3-cubicweb-CUBENAME` instead of just `cubicweb-CUBENAME` (which is still the source package). * Populate Depends using dh_python3 support for Python requirements. * Run test suite at build time using pytest. * Add autopkgtest to run test suite against the installed package. * Bump Standards-Version to 4.3.0.

Source: %(distname)s
Section: web
Priority: optional
Maintainer: %(author)s <%(author-email)s>
Build-Depends:
 debhelper (>= 9),
 dh-python,
 python3-all,
 python3-setuptools,
 python3-pytest,
Standards-Version: 4.3.0
X-Python3-Version: >= 3.4

Package: python3-%(distname)s
Architecture: all
Depends:
 ${python3:Depends},
 ${misc:Depends},
Description: %(shortdesc)s
 CubicWeb is a semantic web application framework.
 .
 %(longdesc)s
 .
 This package will install all the components you need to run an application
 using the %(distname)s cube.