PIM-1957: Move Channel constraint to BaseConnectorBundle
PIM-1957: Move import validator from ImportExportBundle to BaseConnectorBundle
PIM-1957: Move validators DI in BaseConnectorBundle
PIM-1957: Move classes to avoid dependencies
PIM-1957: Update processors
Merge pull request #684 from akeneo/PIM-1957

PIM-1957: Move Channel constraint to BaseConnectorBundle