create a test app that demonstrates the use of jdbcBatchlet, jdbcItemWriter, and jdbcItemReader in a sample job.

There are already tests under jberet-support module for all the 3 components, but these tests focus more on verifying various configurations. Therefore, we need a test app that put all the 3 components together, straightforward without being cluttered with all the configuration options. It can also serve as a testing template for various jdbc-related batch jobs.