[Companion] Show custom control names throughout the UI (& internal refactoring) (#4693)

* [Companion] Introduce new Boards class to further consolidate hardware metadata and remove some globals.

* [Companion] * RawSource::toString() and RawSwitch::toString() can now return custom hardware names (if given a GeneralSettings object) for the following types (respectively):
    SOURCE_TYPE_STICK, SOURCE_TYPE_SWITCH, SWITCH_TYPE_SWITCH, & SWITCH_TYPE_MULTIPOS_POT;
* RawSource::isPot() and isSlider() can now return their own index position in potConfig[]/sliderConfig[];
* Switch indicator strings can be localized if necessary.

* [Companion] Refactor model printers to use new RawSource/RawSwitch capabilities; Simplify model-to-printer mapping scheme in multimodelprinter; Use const ModelData pointer.

* [Companion] Refactor how RawSource and RawSwitch selection combo boxes are populated, using cache-able data models instead of direct manipulation; Refactor some other Helpers function into their own namespace.

* Cosmetics & forgotten qualifier.

companion/src/modelprinter.h

@@ -53,14 +53,14 @@ class ModelPrinter: public QObject
   public:
     ModelPrinter(Firmware * firmware, const GeneralSettings & generalSettings, const ModelData & model);
     virtual ~ModelPrinter();
-  
+
     QString printEEpromSize();
     QString printTrimIncrementMode();
     QString printThrottleTrimMode();
     static QString printModuleProtocol(unsigned int protocol);
     static QString printMultiRfProtocol(int rfProtocol, bool custom);
     static QString printMultiSubType(int rfProtocol, bool custom, unsigned int subType);
-    QString printFlightModeSwitch(int index);
+    QString printFlightModeSwitch(const RawSwitch & swtch);
     QString printFlightModeName(int index);
     QString printFlightModes(unsigned int flightModes);
     QString printModule(int idx);