MC-108: Add an option to avoid generating category URL_KEY.
MC-108: Ensure that url_key is not send if Magento is supposed to handle it.
Merge pull request #333 from akeneo/MC-108

MC-108: Add an option to avoid generating category URL_KEY.
MC-132: Display correctly job_execution.summary during export and in exports history
MC-132: Update Cleaners too.