Cleanup error printing routines

Clean up so that only the following error related printing functions are
used: tio_error_printf(), tio_error_printf_silent(),
tio_warning_printf().

A session mode switch is introduced for error printing so that it will
print error messages with better formatting depending on in or out of
session.

src/main.c

@@ -88,6 +88,9 @@ int main(int argc, char *argv[])
     /* Initialize ANSI text formatting (colors etc.) */
     print_init_ansi_formatting();
 
+    /* Change error printing mode */
+    error_enter_session_mode();
+
     /* Print launch hints */
     tio_printf("tio v%s", VERSION);
     if (interactive_mode)