For performance analysis, it is mandatory to keep logs for a very long
time. Also it is sometimes required to analyse a bug that happened
more than one more ago, so we have no other choices than keep logs
and not remove them.

It includes fixes for step2 of CR1108 deployment.

This reverts commit da8b21dd.

Proper way of handling branch based production environment have to be found.

It is the same as Dublin, but not buggy.

zope.conf is read quite lite during zope startup and some modules are using
environment variables to be set up (like DateTime) *before* zope.conf is read.

Need to allow from www.owlfish.com, as WSGIUtils is available there.

On each zope, configure the zodb_cache_size and zeo_client_cache_size

Goal is to make it smaller to be more readable

Event log to info allows to extract usefull informations for reporting.

Slow system is not a valid state, so, fail early.