Hopefully fixing logging dependency

Author: sebastian-peter

src/main/java/edu/ie3/util/quantities/PowerSystemUnits.java

@@ -10,6 +10,7 @@
 import edu.ie3.util.quantities.interfaces.*;
 import java.util.HashSet;
 import java.util.logging.Level;
+import java.util.logging.Logger;
 import javax.measure.MetricPrefix;
 import javax.measure.Unit;
 import javax.measure.quantity.*;
@@ -31,6 +32,8 @@
  */
 public class PowerSystemUnits extends Units {
 
+  private static final Logger logger = Logger.getLogger(PowerSystemUnits.class.getName());
+
   /* ==== Basic non electric units ==== */
   /** Kilometre */
   public static final Unit<Length> KILOMETRE = MetricPrefix.KILO(METRE);