Added ADC values conversions in the ExperimentData_s structure.

ExperimentData_s: Added functions to translate the ADC values in real
                  world quantities.

GraphTab: The graphs now display the real measured values by calling
          the new functions in ExperimentData_s.
          Added auto-range modification on the X axis.
          Added a 'clear()' slot to erase all graphs.

QSerialListener: All data is now saved in a QVector. Added the
                 'clearRecordedData' and 'saveRecordedData' slots.
Added a Save File menu and minor fixes.

The save file menu allows the user to save data to a .csv file.
Minor fixes for unit conversion.