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/mod.rs

@@ -0,0 +1,8 @@
+// The starting point (Main View).
+pub mod main_view;
+
+/// Receiver widget
+pub mod receiver;
+
+/// Sender widget.
+pub mod sender;