Refactor: Make decompression threads daemons

CityDoctorParent/Extensions/CityDoctorGUI/src/main/java/de/hft/stuttgart/citydoctor2/gui/ZipEntryManager.java

@@ -160,6 +160,7 @@ public class ZipEntryManager {
                     populateZipEntryList(entryList.getSelectionModel().getSelectedIndex());
                 });
             });
+            t.setDaemon(true);
             t.start();
 
         });
@@ -216,6 +217,7 @@ public class ZipEntryManager {
                     populateZipEntryList(entryList.getSelectionModel().getSelectedIndex());
                 });
             });
+            t.setDaemon(true);
             t.start();
         });