Switched to Java based configuration

Hi!

This is my first Pull request and just a proposal. Feel free to ignore this.
I removed the remaining Spring XML configuration, updated the Spring repository link and updated also Spring Batch and Gradle.

I have two configurations, AppConfig (Infrastructure) and ExampleConfiguration (Batch). In contrast to your originally solution the ExampleConfiguration includes the AppConfig (so I changed the direction of dependency). The reason for this was that in an typically application you have one infrastructure and many batches and run the code with the desired batch configuration.

Anyway, thanks for your work!
Kind regards, Christian