Major improvements to the settings API

* Allow the raw structure to be manipulated from C and Legacy APIs

 * Structure is now split between what's on the device and what's on the client so changes will not be visible from read methods until apply()

 * Allow devices to connect which have slightly different firmware versions than the settings structure

include/icsneo/device/valuecan3/valuecan3settings.h

@@ -38,6 +38,8 @@ public:
 	ValueCAN3Settings(std::shared_ptr<Communication> com) : IDeviceSettings(com, sizeof(valuecan3_settings_t)) {}
 	const CAN_SETTINGS* getCANSettingsFor(Network net) const override {
 		auto cfg = getStructurePointer<valuecan3_settings_t>();
+		if(cfg == nullptr)
+			return nullptr;
 		switch(net.getNetID()) {
 			case Network::NetID::HSCAN:
 				return &(cfg->can1);