Add a processor to merge other outputs into a single JRDataSource object.

The MergeDataSourceProcessor allows several datasource to be merged into one for use in a Jasper report detail section.

 An example use case is where we might have zero or many of tables and zero or many legends.  You can configure the template with a detail section that contains a subreport, the name of which is a field in the DataSources and the DataSources for the sub-template another field.  Then you can merge the legend and the tables into a single DataSources.  This way the report will nicely expand depending on if you have a legend and how many tables you have in your report.