Add support to customize transaction attributes

[fmbenhassine]

While the JobRepositoryFactoryBean provides a way to customize the transaction manager to use in the transactional proxy around the JobRepositoy it creates, it does not however allow the customization of transaction attributes.

The goal of this feature request is to make the transaction attributes configurable as well, without changing the current default attributes.

This should also be applied to the JobExplorerFactoryBean (#1307) and JobOperatorFactoryBean (#1078).