Feat: Add button setup

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

@@ -96,8 +96,15 @@ public class ZipEntryPicker {
         entryList.getSelectionModel().selectedItemProperty().addListener((obs, oldI, newI) -> {
             if (newI != null) {
                 showMetadata(newI.getEntry());
+                // Disable loadBtn when entry is erroneous
+                loadBtn.setDisable(newI.getEntry().getErrorType() != null);
             }
         });
+        cancelBtn.setOnAction(e -> stage.close());
+        loadBtn.setOnAction(e -> {
+            CityGmlZipEntry entry = entryList.getSelectionModel().getSelectedItem().getEntry();
+
+        });
     }
 
     public void initialize() {