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/drivers/bmv2/BUILD b/drivers/bmv2/BUILD
index 9478b50..2b42bdb 100644
--- a/drivers/bmv2/BUILD
+++ b/drivers/bmv2/BUILD
@@ -4,7 +4,7 @@
     "//pipelines/basic:onos-pipelines-basic",
     "//protocols/p4runtime/api:onos-protocols-p4runtime-api",
     "//protocols/p4runtime/model:onos-protocols-p4runtime-model",
-    "//lib:io_grpc_grpc_core_context",
+    "//lib:io_grpc_grpc_api_context",
     "//lib:io_grpc_grpc_netty",
     "@minimal_json//jar",
     # "//protocols/bmv2/thrift-api:onos-protocols-bmv2-thrift-api",