Event history service and CLI

- Tool created while debugging ONOS-3509

  Usage Example: (See recent Mastership and Device events)
   onos> events -m -d

Change-Id: I87aceaf8fe61732a61c2d1e39399d0f10a729b54
diff --git a/apps/pom.xml b/apps/pom.xml
index 4d35b4b..b536c7c 100644
--- a/apps/pom.xml
+++ b/apps/pom.xml
@@ -63,6 +63,7 @@
         <module>pathpainter</module>
         <module>drivermatrix</module>
         <module>cpman</module>
+        <module>events</module>
   </modules>
 
     <properties>
@@ -107,3 +108,4 @@
     </build>
 
 </project>
+