Added air pressure

Added this class to the code and also to the main.

Barometer.java

@@ -0,0 +1,44 @@
+import java.util.ArrayList;
+
+public class Barometer extends Grootheid{
+    public ArrayList<Double> list;
+    
+    //constructor
+    public Barometer(Measurement measurement1, ArrayList<Measurement> measurement2){
+        list = new ArrayList<Double>();
+        updateRecent(measurement1);
+        update24Hour(measurement2);
+    }
+
+    
+    public void updateRecent(Measurement measurement1){
+        setCurrent(measurement1.getBarometer());
+    }
+    public void update24Hour(ArrayList<Measurement> measurement2){
+        createList(measurement2);
+        calculateMaxMinAvg(list);
+    }
+    
+    public void display(){
+        super.display();
+        GUIboard.writePageToMatrix("Luchtdruk", "Gemiddelde: " + getAvg(), "");
+    }
+    
+    public void displayGraph()
+    {
+        GUIboard.writeGraphToMatrix(list, getMin(), getMax());
+    }
+    
+    private void createList(ArrayList<Measurement> measurement2)
+    {
+        if(!list.isEmpty())
+        {
+            list.clear();
+        }
+        
+        for(Measurement ms : measurement2)
+        {
+            list.add(ms.getBarometer());
+        }
+    }
+}