Now statuses have different colors. Various minor fixes

CanController.h

@@ -1,6 +1,8 @@
 #ifndef CANCONTROLLER_H
 #define CANCONTROLLER_H
 
+#include <type_traits>
+
 #include <QObject>
 #include <QVariant>
 #include <QDateTime>
@@ -57,7 +59,24 @@ private:
 	void initializeBatteries();
 
 	QList<quint16> registerAddresses() const;
-	QVariant parameterToVariant(quint16 parameter) const;
+
+	template<typename T>
+	static QVariant doubleParameterToVariant(T parameter)
+	{
+		return isParameterEmpty(parameter) ? QVariant() : QVariant::fromValue(parameter / 10.0);
+	}
+
+	template<typename T>
+	static QVariant intParameterToVariant(T parameter)
+	{
+		return isParameterEmpty(parameter) ? QVariant() : QVariant::fromValue(parameter);
+	}
+
+	template<typename T>
+	static bool isParameterEmpty(T /*parameter*/)
+	{
+		return std::numeric_limits<T>::max();
+	}
 
 private:
 	bool isConnected_ = false;