[pkg] various fixes - add missing files to MANIFEST - exclude doc/changes from dh_installchangelogs (it's a directory, which dh_installchangelogs doesn't expect) - fix doc build in debian package

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances