VOL-1460 Updated core to use voltha-protos instead of local protos
Moved protos to python directory in order to maintain functionaly of containers built there.
Added capability to do local builds of protos
Added instructions on running dep ensure for getting protos.
Updated github.com/golang/protobuf version to v1.3.1

Change-Id: Ia6ef55f07f0d5dcb5b750d7c37b21b71db85bfc4
diff --git a/Makefile b/Makefile
index 97624e0..b0bf2be 100644
--- a/Makefile
+++ b/Makefile
@@ -84,6 +84,10 @@
 containers: base rw_core ro_core simulated_olt simulated_onu afrouter arouterd
 
 base:
+ifdef LOCAL_PROTOS
+	mkdir -p vendor/github.com/opencord/voltha-protos/go
+	cp -r ${GOPATH}/src/github.com/opencord/voltha-protos/go/ vendor/github.com/opencord/voltha-protos
+endif
 	docker build $(DOCKER_BUILD_ARGS) -t base:latest -f docker/Dockerfile.base .
 
 afrouter: