BATCHADM-152: Added Batch Job Execution Exit Message on Job Execution Details page

Fix for this feature request: https://jira.springsource.org/browse/BATCHADM-152

This is a useful field for showing a simple log message regarding the batch's final progress, such as "Imported 100 records"

![BATCHADM-152](https://f.cloud.github.com/assets/327741/235529/e0ae02f0-87ad-11e2-8769-e3c4cb37a76f.png)