remove unused radio button preference code

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

src/main/java/com/owncloud/android/ui/RadioButtonPreference.java

@@ -1,38 +0,0 @@
-/**
- * ownCloud Android client application
- *
- * Copyright (C) 2015 ownCloud Inc.
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2,
- * as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-package com.owncloud.android.ui;
-
-import android.content.Context;
-import android.preference.CheckBoxPreference;
-import android.view.View;
-
-import com.owncloud.android.R;
-
-public class RadioButtonPreference extends CheckBoxPreference implements View.OnLongClickListener {
-
-    public RadioButtonPreference(Context context) {
-        super(context, null, android.R.attr.checkBoxPreferenceStyle);
-        setWidgetLayoutResource(R.layout.preference_widget_radiobutton);
-    }
-
-    @Override
-    public boolean onLongClick(View v) {
-        return true;
-    }
-}

src/main/res/layout/preference_widget_radiobutton.xml

@@ -1,21 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright (C) 2006 The Android Open Source Project
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-http://www.apache.org/licenses/LICENSE-2.0
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
--->
-<!-- Layout used by CheckBoxPreference for the checkbox style. This is inflated
-inside android.R.layout.preference. -->
-<RadioButton xmlns:android="http://schemas.android.com/apk/res/android"
-android:id="@+android:id/checkbox"
-android:layout_width="wrap_content"
-android:layout_height="wrap_content"
-android:layout_gravity="center"
-android:focusable="false"
-android:clickable="false" />