In preparation for dynamic clustering support:
- Added Cluster metadata service and metadata store interfaces
- Added a static cluster metadata store implementation that is backed by a local file.
- Consolidated the existing cluster.json and tablets.json metadata files into a single cluster.json file that has all the cluster related metadata.
- Removed dependency on ONOS_NIC env variable.

Change-Id: Ia0a8bb69740caecdcdde71a9408be37c56ae2504
diff --git a/core/api/src/main/java/org/onosproject/cluster/Partition.java b/core/api/src/main/java/org/onosproject/cluster/Partition.java
new file mode 100644
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+++ b/core/api/src/main/java/org/onosproject/cluster/Partition.java
@@ -0,0 +1,64 @@
+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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 org.onosproject.cluster;
+
+import java.util.Collection;
+import java.util.Set;
+
+import com.google.common.collect.ImmutableSet;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * A data partition.
+ * <p>
+ * Partition represents a slice of the data space and is made up of a collection
+ * of {@link org.onosproject.cluster.ControllerNode nodes}
+ * that all maintain copies of this data.
+ */
+public class Partition {
+
+    private final String name;
+    private final Set<NodeId> members;
+
+    private Partition() {
+        name = null;
+        members = null;
+    }
+
+    public Partition(String name, Collection<NodeId> members) {
+        this.name = checkNotNull(name);
+        this.members = ImmutableSet.copyOf(checkNotNull(members));
+    }
+
+    /**
+     * Returns the partition name.
+     * <p>
+     * Each partition is identified by a unique name.
+     * @return partition name
+     */
+    public String getName() {
+        return this.name;
+    }
+
+    /**
+     * Returns the collection of controller node identifiers that make up this partition.
+     * @return collection of controller node identifiers
+     */
+    public Collection<NodeId> getMembers() {
+        return this.members;
+    }
+}
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