#654 - Partial work for the LED/Speaker.

Framework is done. Just need to blink a few things and update protobufs.

src/plugins/ExternalNotificationPlugin.h

@@ -0,0 +1,43 @@
+#pragma once
+
+#include "SinglePortPlugin.h"
+#include "concurrency/OSThread.h"
+#include "configuration.h"
+#include <Arduino.h>
+#include <functional>
+
+
+class ExternalNotificationPlugin : private concurrency::OSThread
+{
+    bool firstTime = 1;
+
+  public:
+    ExternalNotificationPlugin();
+
+  protected:
+    virtual int32_t runOnce();
+};
+
+extern ExternalNotificationPlugin *externalNotificationPlugin;
+
+/*
+ * Radio interface for ExternalNotificationPlugin
+ *
+ */
+class ExternalNotificationPluginRadio : public SinglePortPlugin
+{
+
+  public:
+    ExternalNotificationPluginRadio() : SinglePortPlugin("ExternalNotificationPluginRadio", PortNum_TEXT_MESSAGE_APP) {}
+
+  protected:
+    virtual MeshPacket *allocReply();
+
+    /** Called to handle a particular incoming message
+
+    @return true if you've guaranteed you've handled this message and no other handlers should be considered for it
+    */
+    virtual bool handleReceived(const MeshPacket &mp);
+};
+
+extern ExternalNotificationPluginRadio *externalNotificationPluginRadio;