Introduce CCR container class

This commit introduces the container class for CCR functionality. Future
work will expose more specific CCR functionality to the X-Pack plugin
through this class.

Relates #2704

x-pack/plugin/src/main/java/org/elasticsearch/xpack/ccr/Ccr.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.ccr;
+
+import org.elasticsearch.common.settings.Setting;
+import org.elasticsearch.common.settings.Settings;
+
+import java.util.List;
+
+import static org.elasticsearch.xpack.ccr.CcrSettings.CCR_ENABLED_SETTING;
+
+/**
+ * Container class for CCR functionality.
+ */
+public final class Ccr {
+
+    @SuppressWarnings("unused,FieldCanBeLocal")
+    private final boolean enabled;
+
+    /**
+     * Construct an instance of the CCR container with the specified settings.
+     *
+     * @param settings the settings
+     */
+    public Ccr(final Settings settings) {
+        this.enabled = CCR_ENABLED_SETTING.get(settings);
+    }
+
+    /**
+     * The settings defined by CCR.
+     *
+     * @return the settings
+     */
+    public List<Setting<?>> getSettings() {
+        return CcrSettings.getSettings();
+    }
+
+}

x-pack/plugin/src/main/java/org/elasticsearch/xpack/ccr/CcrSettings.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.ccr;
+
+import org.elasticsearch.common.settings.Setting;
+import org.elasticsearch.common.settings.Setting.Property;
+
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Container class for CCR settings.
+ */
+final class CcrSettings {
+
+    // prevent construction
+    private CcrSettings() {
+
+    }
+
+    /**
+     * Setting for controlling whether or not CCR is enabled.
+     */
+    static final Setting<Boolean> CCR_ENABLED_SETTING = Setting.boolSetting("xpack.ccr.enabled", true, Property.NodeScope);
+
+    static List<Setting<?>> getSettings() {
+        return Collections.singletonList(CCR_ENABLED_SETTING);
+    }
+
+}