[doc] fix reference to ~src/cubes in tutorial ~src/cubes refer to the $HOME/cubes directory of "src" user while ~/src/cubes refer to $HOME/src/cubes directory of current user.

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