[test] Use --short-description when testing newcube command

[devtools] Allow to specify short desc on `newcube` command line In order to implement automated testing of `cubicweb-ctl newcube`, we need to avoid any user interaction. So we add a `-s` switch to specify a short description on the command-line instead of requiring an input.

[pkg] Add new autopkgtest for skeleton packaging When running `cubicweb-ctl newcube`, the generated template provides debian packaging. So let's add automated tests for that using autopkgtest. The new test will generated a new cube, build a source tarball, build the package, try to install it, see if the Python 3 module is available and even run autopkgtest against the newly created packages. Along the way it will also print information about the generated package: buildinfo, package content, and lintian report.

[cubicweb-ctl] move to accepting only once instance name per command The rationals behind this decision are: - while in the past managing all instances sytem wide made a lot of sens, pratices have evolved today and we've moved to managing one instance by one - this makes things easier to debug since commands since using them on several instances were making this harder (errors hidden in the middle) - also solve the problem of the return code to have, before it was always 0 which prevented to do things like: ipython --pdb $(which cubicweb-ctl) $command $instance or shell scripts that used it - this simplify the code and is always good to take