[Simulator] Further improvements (reload radio, momentary switches, etc.) (#4303)

* [Simulator] Add ability to reload all radio data w/out exiting simulator (will also adjust UI for any hardware changes); Refactor how keymap help text is generated.

* [Simulator] Only update channel/logical switch/GVar output displays if the corresponding tab is actually visible (further CPU usage reductions).

* [Simulator] Implement momentary toggle switches with "latch" function.

* [Simulator] Mouse wheel event over multi-position knobs now properly rotates them to detent positions.

* [Simulator] Fix mouse wheel event propagation after multi-position knob rotation; Cosmetics.

* [Simulator] Internals: Greatly improve object cleanup on exit; Refactor SimulatedUIWidget timer event triggering.

* [Simulator] Fix throttle stick position/lock not being set properly upon repeated launches from Companion.

* [Simulator] Fix build w/out SDL. KnobWidget cleanup.

* [Companion] Do NOT delete SimulatorInterface on simulator dialog exit (fix possible crash on dialog close).

* [Simulator] Ensure joystick is NULL at start.

* [Simulator] Fix/improve color blending on 4-bit screens with different BG colors; Cosmetics.

* [Simulator] Fix LCD screenshot folder path; Fix timer slot for Qt backwards compatibility.

* [TravisCI] Set Qt version to 5.3 to match release build servers.

* Fixed segfault when saving setup with no models defined [Horus]

* Fixed radio data import [Horus] (broken in 0f90ff0b65)

* [Simulator] Always keep toggle switch active while held with mouse button.

companion/src/simulation/simulateduiwidget.h

@@ -62,7 +62,7 @@ class SimulatedUIWidget : public QWidget
 
   public slots:
 
-    void timedUpdate(unsigned loop);
+    void updateUi();
     void saveScreenshot(int idx = -1);
     void captureScreenshot() { saveScreenshot(); }
     void simulatorWheelEvent(qint8 steps);