fix schema migration hooks (partial) SQL Server requires some additional steps to alter columns (index drop and restore, etc...) and this in turn requires passing a connection on the DB to find out the indexes. Also partially fix an issue where the null_allowed value was not correctly computed. Still some problems in there (see https://www.logilab.net/cwo/ticket/1109558)

usr/lib/python2.4/site-packages/cubicweb/
etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/run/cubicweb
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances