Revisit the configuration code of EnableBatchProcessing

Before this commit, the configuration of infrastructure beans
was confusing and not straightforward to customize. This commit
changes the way Batch infrastructure beans are configured.
The most important changes are:

* EnableBatchProcessing now provides new attributes to
configure properties of infrastructure beans
* Bean registration is now done programmatically with a
BeanDefinitionRegistrar instead of importing a class with
statically annotated bean definition methods
* Bean are now resolved from the application context directly
instead of being resolved from a BatchConfigurer
* Both a data source and a transaction manager are now
required to be defined in the application context
* AbstractBatchConfiguration is now intended to be extended
by users code to get/customize basic infrastructure beans

Issue #3942

Author: fmbenhassine

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/support/AbstractBatchConfiguration.java

@@ -236,7 +236,7 @@ protected boolean getValidateTransactionState() {
 	/**
 	 * Return the transaction isolation level when creating job executions. Defaults to
 	 * {@link Isolation#SERIALIZABLE}.
-	 * @returnReturn the transaction isolation level when creating job executions
+	 * @return the transaction isolation level when creating job executions
 	 */
 	protected Isolation getIsolationLevelForCreate() {
 		return Isolation.SERIALIZABLE;
@@ -250,15 +250,15 @@ protected Isolation getIsolationLevelForCreate() {
 	 * databases with multi-byte character sets this number can be smaller (by up to a
 	 * factor of 2 for 2-byte characters) than the declaration of the column length in the
 	 * DDL for the tables. Defaults to
-	 * {@link AbstractJdbcBatchMetadataDao.DEFAULT_EXIT_MESSAGE_LENGTH}
+	 * {@link AbstractJdbcBatchMetadataDao#DEFAULT_EXIT_MESSAGE_LENGTH}
 	 */
 	protected int getMaxVarCharLength() {
 		return AbstractJdbcBatchMetadataDao.DEFAULT_EXIT_MESSAGE_LENGTH;
 	}
 
 	/**
 	 * Return the prefix of Batch meta-data tables. Defaults to
-	 * {@link AbstractJdbcBatchMetadataDao.DEFAULT_TABLE_PREFIX}.
+	 * {@link AbstractJdbcBatchMetadataDao#DEFAULT_TABLE_PREFIX}.
 	 * @return the prefix of meta-data tables
 	 */
 	protected String getTablePrefix() {