Add getters for DAOs in SimpleJobExplorer

[spring-projects-issues]

Gérald Quintana opened BATCH-1994 and commented

SimpleJobExplorer can not easily be extended because jobInstanceDao, jobExecutionDao, stepExecutionDao, ecDao are private fields.

Add public (or at least protected) getters to theses Daos, to make them accessible to sub-classes

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Affects: 2.1.9