Rudder

Following #2295, we will need to update the existing events log in database to change from old names to new ones.

That could be done thanks to Postgres XML functions (see: http://www.postgresql.org/docs/9.1/static/xml2.html) or a custom Scala script.

It will be done when the webapp starts, and look for the lowest version of fileFormat in base (see #2363 and #2364). Depending on them, compared to the required fileFormat, the script will update the database.