First attempt at supporting builds with Java 11

Includes:
- Bump protobuf to 3.8.0 and grpc-java to 1.21.0 (along with transitive
  dependencies such as Netty)
- Add jaxb_api at compile time when needed (removed in JDK 11)
- Bump Bnd to 4.1 (adds support for Java 11)

To build with JDK 11, uncomment lines in .bazelrc.
Tested with Bazel 0.26.0.

Change-Id: Ib8e0c7310eacf97328762606e57c01e4834e5565
diff --git a/apps/castor/BUILD b/apps/castor/BUILD
index 546453b..d493321 100644
--- a/apps/castor/BUILD
+++ b/apps/castor/BUILD
@@ -2,6 +2,7 @@
     "//core/store/serializers:onos-core-serializers",
     "//apps/routing-api:onos-apps-routing-api",
     "//apps/intentsync:onos-apps-intentsync",
+    "@jaxb_api//jar",
 ]
 
 BUNDLES = [