Require double confirmation for deleting all transactions

The user must check a checkbox to enable the delete button. This tries
to avoid confirming irreversible actions by mistake.

Fixes codinguser#544

app/src/main/java/org/gnucash/android/ui/settings/dialog/DeleteAllTransactionsConfirmationDialog.java

@@ -16,13 +16,11 @@
  */
 package org.gnucash.android.ui.settings.dialog;
 
-import android.app.AlertDialog;
 import android.app.Dialog;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.os.Bundle;
 import android.support.annotation.NonNull;
-import android.support.v4.app.DialogFragment;
 import android.util.Log;
 import android.widget.Toast;
 
@@ -44,7 +42,7 @@
  * @author ngewif <ngewif@gmail.com>
  * @author Yongxin Wang <fefe.wyx@gmail.com>
  */
-public class DeleteAllTransactionsConfirmationDialog extends DialogFragment {
+public class DeleteAllTransactionsConfirmationDialog extends DoubleConfirmationDialog {
 
     public static DeleteAllTransactionsConfirmationDialog newInstance() {
         DeleteAllTransactionsConfirmationDialog frag = new DeleteAllTransactionsConfirmationDialog();
@@ -53,7 +51,7 @@ public static DeleteAllTransactionsConfirmationDialog newInstance() {
 
     @Override
     @NonNull public Dialog onCreateDialog(Bundle savedInstanceState) {
-        return new AlertDialog.Builder(getActivity())
+        return getDialogBuilder()
                 .setIcon(android.R.drawable.ic_delete)
                 .setTitle(R.string.title_confirm_delete).setMessage(R.string.msg_delete_all_transactions_confirmation)
                 .setPositiveButton(R.string.alert_dialog_ok_delete,
@@ -80,19 +78,6 @@ public void onClick(DialogInterface dialog, int whichButton) {
                             }
                         }
 
-                )
-                .
-
-                        setNegativeButton(R.string.alert_dialog_cancel,
-                                new DialogInterface.OnClickListener() {
-                                    public void onClick(DialogInterface dialog, int whichButton) {
-                                        dismiss();
-                                    }
-                                }
-
-                        )
-                .
-
-                        create();
+                ).create();
     }
 }