Stash radio settings per app (#1151)

* add a little Stash utility.
* add radio state RAII helper.
* first part of radio_state changes
* add radio_state_ to rest of apps
* fix freq_step and format
* fix unused ui_sigfrx: corrected sample rate, added back freq setting

firmware/application/apps/lge_app.cpp

@@ -243,8 +243,7 @@ void LGEView::start_tx() {
         tx_view.on_show();  // Refresh tuning frequency display
         tx_view.set_dirty();
     }
-    transmitter_model.set_sampling_rate(2280000);
-    transmitter_model.set_baseband_bandwidth(1750000);
+
     transmitter_model.enable();
 
     chThdSleep(100);