ENH: Add Query findEach() with batch consumer

This is a variation of findEach() that makes it easy to have a batch consumer processing a large result in batches.  For example, process in batches of 50 beans.

Note that the last batch consumed/processed will often have less than the batch size.

ebean-core/src/test/java/io/ebeaninternal/api/TDSpiEbeanServer.java

@@ -675,6 +675,10 @@ public class TDSpiEbeanServer implements SpiEbeanServer {
   public <T> void findEach(Query<T> query, Consumer<T> consumer, Transaction transaction) {
   }
 
+  @Override
+  public <T> void findEach(Query<T> query, int batch, Consumer<List<T>> consumer, Transaction t) {
+  }
+
   @Override
   public <T> void findEachWhile(Query<T> query, Predicate<T> consumer, Transaction transaction) {
   }