Refactoring, housekeeping, documentation

Add a class diagram. Still needs some details.
Refactor to better respect SOLID principles.
Housekeeping, move and rename classes/files.

app/src/sensor/LMSensor.cxx

@@ -0,0 +1,26 @@
+#include <boost/json/kind.hpp>
+#include <sensor/LMSensor.h>
+#include <sensors/sensors.h>
+
+using namespace std;
+
+LMSensor::LMSensor(const sensors_chip_name *chipName,
+                   const sensors_feature *feature,
+                   const sensors_subfeature *subfeature)
+    : mChipName(chipName), mFeature(feature), mSubFeature(subfeature) {}
+
+int LMSensor::value() {
+  double value;
+  sensors_get_value(mChipName, mSubFeature->number, &value);
+
+  return static_cast<int>(value);
+}
+
+const string LMSensor::toString() const {
+  return sensors_get_label(mChipName, mFeature);
+}
+
+json LMSensor::toJson() const {
+  json obj = {"HwmonSensor", toString()};
+  return obj;
+}