Improve use of MAVSDK::add_any_connection()

Added error printing and possibility to use UART as connection
to the flight controller.

Issue: https://denyspopov.atlassian.net/browse/AZ-16
Type: New Feature

src/az_config.h

@@ -1,6 +1,5 @@
 #pragma once
 
-#define FUNCTION_NAME(func) func()
-
-const char *AZ_CONNECTION          = "udp://:14550";
+const char *AZ_CONNECTION_SERIAL   = "serial:///dev/ttyS0:115200";
+const char *AZ_CONNECTION_UDP      = "udp://:14550";
 const int AZ_RELATIVE_FLY_ALTITUDE = 50;