advotracker: reorganize the project using a crate based structure

* advotracker: the framework project
* crate/advotrackerdb: implementation of the database backend
* crate/advotrackerd: implementation of the backend (daemon)
* crate/adovtracker: implementaton of the application (CLI and GUI)

Signed-off-by: Ralf Zerres <ralf.zerres@networkx.de>

crates/advotracker_client/examples/messages_test/main.rs

@@ -0,0 +1,32 @@
+/*
+ * OrbTK - The Orbital Widget Toolkit
+ *
+ * Copyright 2021 Ralf Zerres <ralf.zerres@networkx.de>
+ * SPDX-License-Identifier: (0BSD or MIT)
+ */
+
+use orbtk::prelude::*;
+
+mod main_view;
+mod receiver;
+mod sender;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // use this only if you want to run it as web application.
+    orbtk::initialize();
+
+    Application::new()
+        .window(|ctx| {
+            Window::new()
+                .name("Main")
+                .title("OrbTK: example send/receive messages")
+                .position((100.0, 100.0))
+                .resizeable(true)
+                .size(450.0, 500.0)
+                .child(main_view::MainView::new().build(ctx))
+                .build(ctx)
+        })
+        .run();
+
+    Ok(())
+}