BATCH-2144 Convert Spring Batch to use Gradle

* Use Gradle 1.11
* Remove SpringSource references
* Update JavaDoc overview
* Update Jacoco conf + Add license/manifest files
* Addresses also BATCH-2187
* Update a number of unit tests to not be ignored

Jira: https://jira.springsource.org/browse/BATCH-2144
BATCH-2144 - Merged Michael's changes

* Merge PR https://github.com/ghillert/spring-batch/pull/1
* Update Spring Integration dependency to 4.0.0.RC1
* Update docbook-reference-plugin to 0.2.8