Updated the logger subscriber to handle invalid item events
Dispatch invalid item exception inside item step
Move Test class of invalid item exception
Throw an exception if the processor returns a null value
Removed useless phpunit group
Added step execution warning supports

Dropped support for (reader|filter|writer) specific warning.
Factorized the warning handling method
Add step execution warning when invalid item encountered
Provided a configuration to enable/disable batch mail notification
Override batch notification recipient email
Validate the email option of the batch command
Fixed batch command validations
Store the step element name instead of classname

This is more usefull for displaying purpose. Classname is still sent
into the InvalidItemEvent, thus being displayed in the log.
Throw invalid item exception in the csv file reader
Updated phpdoc
Fixed Job tests
Merge branch 'maintenance/pim_beta1' into feature/batch-command-emails
Merge pull request #566 from laboro/feature/batch-command-emails

[BatchBundle] Notify job execution through email
Merge branch 'maintenance/pim_beta1' into feature/invalid-item-handling
Merge pull request #560 from laboro/feature/invalid-item-handling

[BatchBundle] Invalid item handling