ERP5 SR: Add Jinja2 to the explicit list of eggs.

Jinja2 is used inside of ERP5 (scalability tests).
So we need to explicitely add it, even if we already download it, otherwise it seems buildout keeps it for its own internal use.
helloworld SR: redirect output to log.

Also improve overall quality.
(cherry picked from commit 7232c1e3409b65790d98d44467e4ef3739940478)
Add squid component.

It seems the only tool supporting http://tools.ietf.org/html/rfc5861
Drop non defined section usage.
Allow to manipulate HTTP headers.
squid: Add Squid to Apache Frontend (Romain)
squid: Add Squid Recipe from erp5-vifib (Romain C.)
apache-frontend: Temp commit before reverse
apache-frontend: Fix instance.cfg for apache frontend, no squid in recipe
squid: Squid use hardcoded domain
apache-frontend: Remove stunnel from apache frontend recipe
squid: Squid use destination ip instead of domain
apache-frontend: Introduce new architecture for apache frontend
apache-frontend: Stop using apache frontend recipes, no more preconfiguration done by apache_frontend, raw apache config is given by master

apache-frontend: remove unused apache_frontend recipe
apache-frontend: Support ssl certificates in apache frontend
apache-frontend: Add promise on apache frontend, its squid and its apache backend
apache-frontend: Small improvments on profile and templates for apache frontend
apache-frontend: Introducing yakari mode for apache-frontend
apache-frontend: Add logrotate for apaches and squid
apache-frontend: introduce default virtualhost with notfound message, add per slave logging