Included setting dft number from gui.

src/signals.rs

@@ -1,5 +1,7 @@
+use crate::icd::IcdDftNum;
+
 #[derive(Copy, Clone)]
 pub enum SingleFrequencySignal {
-    Start(u32),
+    Start(u32, IcdDftNum), // frequency in Hz, DFT number
     Stop,
 }