XD-2172 Parameterize internal Spring Batch JobRepostiory settings

JIRA: https://jira.spring.io/browse/XD-2172

Add the custom `BatchConfigurer` to the batch/batch.xml file to make the `JobRepositoryFactoryBean` settings
available for customization via container properties. 
The Spring XD specific `BatchConfigurer` is a modified copy of the `org.springframework.batch.core.configuration.annotation.DefaultBatchConfigurer`.

This is in order to be able to mock JobRepositoryFactoryBean creation with Mockito in the unit test.