emit + tests for OFPacketProvider

Change-Id: I9d6a2a641f857742fa68597189a9047dd16989d1
diff --git a/openflow/api/src/main/java/org/onlab/onos/openflow/controller/OpenFlowPacketContext.java b/openflow/api/src/main/java/org/onlab/onos/openflow/controller/OpenFlowPacketContext.java
index 9d07c2f..85ea70a 100644
--- a/openflow/api/src/main/java/org/onlab/onos/openflow/controller/OpenFlowPacketContext.java
+++ b/openflow/api/src/main/java/org/onlab/onos/openflow/controller/OpenFlowPacketContext.java
@@ -5,8 +5,9 @@
 
 /**
  * A representation of a packet context which allows any provider
- * to view the packet in event but may block the response to the
- * event if blocked has been called.
+ * to view a packet in event, but may block the response to the
+ * event if blocked has been called. This packet context can be used
+ * to react to the packet in event with a packet out.
  */
 public interface OpenFlowPacketContext {