Detangling incubator: virtual nets, tunnels, resource labels, oh my

- virtual networking moved to /apps/virtual; with CLI & REST API
- tunnels and labels moved to /apps/tunnel; with CLI & REST API; UI disabled for now
- protobuf/models moved to /core/protobuf/models
- defunct grpc/rpc registry stuff left under /graveyard
- compile dependencies on /incubator moved to respective modules for compilation
- run-time dependencies will need to be re-tested for dependent apps

- /graveyard will be removed in not-too-distant future

Change-Id: I0a0b995c635487edcf95a352f50dd162186b0b39
diff --git a/apps/proxyarp/BUILD b/apps/proxyarp/BUILD
index 907c556..72febb4 100644
--- a/apps/proxyarp/BUILD
+++ b/apps/proxyarp/BUILD
@@ -1,6 +1,4 @@
-COMPILE_DEPS = CORE_DEPS + [
-    "//incubator/api:onos-incubator-api",
-]
+COMPILE_DEPS = CORE_DEPS
 
 osgi_jar(
     deps = COMPILE_DEPS,