[doc] Rewrite "pyramid" index page in the book We drop references to pyramid-cubicweb and cubicweb-pyramid, remaining of the merge in 3.24. We now mention the two possible operation modes (with bwcompat being true or false).

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