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/openstacktelemetry/BUILD b/apps/openstacktelemetry/BUILD
index 33b9813..11a1d3d 100644
--- a/apps/openstacktelemetry/BUILD
+++ b/apps/openstacktelemetry/BUILD
@@ -16,7 +16,7 @@
     "@simpleclient_hotspot//jar",
     "@simpleclient_servlet//jar",
     # gRPC dependencies (with patched core)
-    "//lib:io_grpc_grpc_core_context",
+    "//lib:io_grpc_grpc_api_context",
     "//lib:io_grpc_grpc_stub",
     "//lib:io_grpc_grpc_netty",
     "//lib:io_grpc_grpc_auth",