Rename L2 load balancer to port load balancer

CLI commands are also renamed to plbs, plb-add and plb-remove

Change-Id: I4c26b390acc5a961594a1dca92a76bee2148c090
diff --git a/app/BUILD b/app/BUILD
index de9beab..c6844a6 100644
--- a/app/BUILD
+++ b/app/BUILD
@@ -4,7 +4,7 @@
     "//apps/route-service/api:onos-apps-route-service-api",
     "//apps/mcast/api:onos-apps-mcast-api",
     "//apps/mcast/cli:onos-apps-mcast-cli",
-    "//apps/l2lb:onos-apps-l2lb",
+    "//apps/portloadbalancer:onos-apps-portloadbalancer",
 ]
 
 TEST_DEPS = TEST_ADAPTERS + [