Basic console window for digital output

- Probably end up making this a single tabbed dialog but this works for
the moment

src/modules/modem/analog/ModemAM.cpp

@@ -1,6 +1,6 @@
 #include "ModemAM.h"
 
-ModemAM::ModemAM() {
+ModemAM::ModemAM() : ModemAnalog() {
     demodAM = ampmodem_create(0.5, 0.0, LIQUID_AMPMODEM_DSB, 0);
 }