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/vendor/google.golang.org/grpc/keepalive/keepalive.go b/vendor/google.golang.org/grpc/keepalive/keepalive.go
index 899e72d..34d31b5 100644
--- a/vendor/google.golang.org/grpc/keepalive/keepalive.go
+++ b/vendor/google.golang.org/grpc/keepalive/keepalive.go
@@ -33,6 +33,7 @@
 type ClientParameters struct {
 	// After a duration of this time if the client doesn't see any activity it
 	// pings the server to see if the transport is still alive.
+	// If set below 10s, a minimum value of 10s will be used instead.
 	Time time.Duration // The current default value is infinity.
 	// After having pinged for keepalive check, the client waits for a duration
 	// of Timeout and if no activity is seen even after that the connection is
@@ -62,6 +63,7 @@
 	MaxConnectionAgeGrace time.Duration // The current default value is infinity.
 	// After a duration of this time if the server doesn't see any activity it
 	// pings the client to see if the transport is still alive.
+	// If set below 1s, a minimum value of 1s will be used instead.
 	Time time.Duration // The current default value is 2 hours.
 	// After having pinged for keepalive check, the server waits for a duration
 	// of Timeout and if no activity is seen even after that the connection is