Rename jobs.yml config file to batch_jobs.yml and add missing phpdoc
PIM-1645 : update addStepToJob in connector registry to be able to use
custom step that uses custom services and parameters
PIM-1645 : change createStep of step factory to handle the creation of
custom step and not only item step
PIM-1645 : change batch_jobs.yml config parsing to retrieve step class,
custom services and paratemers to use to create a step
PIM-1645 : fix step factory unit test
PIM-1645 : use new jobs definition format