new command <version> to get plugin version

test/client_version.py

@@ -0,0 +1,14 @@
+#!/usr/bin/env python3
+
+import asyncio
+import websockets
+
+async def hello():
+    uri = "ws://localhost:6001"
+    async with websockets.connect(uri) as websocket:
+        await websocket.send('{"jsonrpc": "2.0", "method": "version", "id": 6}')
+        result = await websocket.recv()
+        print("result: ", result)
+
+asyncio.get_event_loop().run_until_complete(hello())
+