Update contentType length
Update contentType length

In some case the contentType can be more than 64 characters, Mysql truncate the string in that case however PostgreSQL throws an exception.
jerome-fix/SonataMediaBundle,hug963/SonataMediaBundle,rmzamora/SonataMediaBundle,hug963/SonataMediaBundle,bgaleotti/SonataMediaBundle,Soullivaneuh/SonataMediaBundle,Soullivaneuh/SonataMediaBundle,jerome-fix/SonataMediaBundle,sonata-project/SonataMediaBundle,nicolasricci/SonataMediaBundle,jerome-fix/SonataMediaBundle,hug963/SonataMediaBundle,bgaleotti/SonataMediaBundle,rmzamora/SonataMediaBundle,vyshkant/SonataMediaBundle,vyshkant/SonataMediaBundle,Soullivaneuh/SonataMediaBundle,nicolasricci/SonataMediaBundle,bgaleotti/SonataMediaBundle,OskarStark/SonataMediaBundle,hug963/SonataMediaBundle,jerome-fix/SonataMediaBundle,OskarStark/SonataMediaBundle,vyshkant/SonataMediaBundle,hug963/SonataMediaBundle,Soullivaneuh/SonataMediaBundle,vyshkant/SonataMediaBundle,vyshkant/SonataMediaBundle,nicolasricci/SonataMediaBundle,rmzamora/SonataMediaBundle,nicolasricci/SonataMediaBundle,nicolasricci/SonataMediaBundle,OskarStark/SonataMediaBundle,bgaleotti/SonataMediaBundle,Soullivaneuh/SonataMediaBundle,OskarStark/SonataMediaBundle