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/python/protos/logical_device.proto b/python/protos/logical_device.proto
new file mode 100644
index 0000000..521768c
--- /dev/null
+++ b/python/protos/logical_device.proto
@@ -0,0 +1,62 @@
+syntax = "proto3";
+
+option go_package = "github.com/opencord/voltha-protos/go/voltha";
+
+package voltha;
+
+import "meta.proto";
+import "google/api/annotations.proto";
+import "openflow_13.proto";
+
+message LogicalPortId {
+    // unique id of logical device
+    string id = 1;
+
+    // id of the port on the logical device
+    string port_id = 2;
+}
+
+message LogicalPort {
+    string id = 1;
+    openflow_13.ofp_port ofp_port = 2;
+    string device_id = 3;
+    uint32 device_port_no = 4;
+    bool root_port = 5;
+    openflow_13.ofp_port_stats ofp_port_stats = 6;
+}
+
+message LogicalPorts {
+    repeated LogicalPort items = 1;
+}
+
+message LogicalDevice {
+
+    // unique id of logical device
+    string id = 1;
+
+    // unique datapath id for the logical device (used by the SDN controller)
+    uint64 datapath_id = 2;
+
+    // device description
+    openflow_13.ofp_desc desc = 3;
+
+    // device features
+    openflow_13.ofp_switch_features switch_features = 4;
+
+    // name of the root device anchoring logical device
+    string root_device_id = 5;
+
+    // logical device ports
+    repeated LogicalPort ports = 128 [(child_node) = {key: "id"}];
+
+    // flows configured on the logical device
+    openflow_13.Flows flows = 129 [(child_node) = {}];
+
+    // flow groups configured on the logical device
+    openflow_13.FlowGroups flow_groups = 130 [(child_node) = {}];
+
+}
+
+message LogicalDevices {
+    repeated LogicalDevice items = 1;
+}