Update SettingsPanel UI

UI changes include:
- RecyclerView to host slices
- Font family to headline font
- Title is now centered
- Added SeeMore & Done buttons
- Horizontal Dividers between slices
- Indented Slices
- Landscape layout is fullscreen

Change-Id: I3549c847fc88edd81f670ddfa2907dd3741441e0
Screenshot: https://screenshot.googleplex.com/RzWktzOZJkc
Test: Robolectric
Test: Manual app
Bug: 118622007

tests/robotests/src/com/android/settings/panel/FakePanelContent.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+
+package com.android.settings.panel;
+
+import static com.android.settings.slices.CustomSliceRegistry.WIFI_SLICE_URI;
+
+import android.content.Intent;
+import android.net.Uri;
+
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Fake PanelContent for testing.
+ */
+public class FakePanelContent implements PanelContent {
+
+    public static final String FAKE_KEY = "fake_key";
+
+    public static final CharSequence TITLE = "title";
+
+    public static final List<Uri> SLICE_URIS = Arrays.asList(
+        WIFI_SLICE_URI
+    );
+
+    public static final Intent INTENT = new Intent();
+
+    @Override
+    public CharSequence getTitle() {
+        return TITLE;
+    }
+
+    @Override
+    public List<Uri> getSlices() {
+        return SLICE_URIS;
+    }
+
+    @Override
+    public Intent getSeeMoreIntent() {
+        return INTENT;
+    }
+}