Require double confirmation for deleting all accounts

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

Fixes #544

Author: rivaldi8

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

@@ -16,13 +16,10 @@
 
 package org.gnucash.android.ui.settings.dialog;
 
-import android.annotation.TargetApi;
-import android.app.AlertDialog;
 import android.app.Dialog;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.os.Bundle;
-import android.support.v4.app.DialogFragment;
 import android.widget.Toast;
 
 import org.gnucash.android.R;
@@ -36,7 +33,7 @@
  *
  * @author Ngewi Fet <ngewif@gmail.com>
  */
-public class DeleteAllAccountsConfirmationDialog extends DialogFragment {
+public class DeleteAllAccountsConfirmationDialog extends DoubleConfirmationDialog {
 
     public static DeleteAllAccountsConfirmationDialog newInstance() {
         DeleteAllAccountsConfirmationDialog frag = new DeleteAllAccountsConfirmationDialog();
@@ -45,7 +42,7 @@ public static DeleteAllAccountsConfirmationDialog newInstance() {
 
     @Override
     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.confirm_delete_all_accounts)
                 .setPositiveButton(R.string.alert_dialog_ok_delete,
@@ -59,13 +56,6 @@ 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();
     }
 }