[ONOS-3648] Implement REST API for collecting system metrics

- Implement REST API for gathering system metrics
- Add unit test for REST API
- Add swagger doc for REST API

Change-Id: Iedd21a5f6ed14d595e4d35c1fa08270b48a5031e
diff --git a/apps/cpman/src/main/resources/definitions/NetworkMetricsPost.json b/apps/cpman/src/main/resources/definitions/NetworkMetricsPost.json
new file mode 100644
index 0000000..f9ad7d3
--- /dev/null
+++ b/apps/cpman/src/main/resources/definitions/NetworkMetricsPost.json
@@ -0,0 +1,31 @@
+{
+  "type": "object",
+  "required": [
+    "incomingBytes",
+    "outgoingBytes",
+    "incomingPackets",
+    "outgoingPackets"
+  ],
+  "properties": {
+    "incomingBytes": {
+      "type": "integer",
+      "format": "int64",
+      "example": "1024"
+    },
+    "outgoingBytes": {
+      "type": "integer",
+      "format": "int64",
+      "example": "1024"
+    },
+    "incomingPackets": {
+      "type": "integer",
+      "format": "int64",
+      "example": "1000"
+    },
+    "outgoingPackets": {
+      "type": "integer",
+      "format": "int64",
+      "example": "2000"
+    }
+  }
+}
\ No newline at end of file