Ensure Compaction workload is stored in write-once meta-data files separate from timeline files.

This avoids concurrency issues when compactor(s) and ingestor are running in parallel.
    In the Next PR -> Safety concern regarding Cleaner retaining all meta-data and file-slices for pending compactions will be addressed

hoodie-client/src/main/java/com/uber/hoodie/io/compact/HoodieCompactionInstantWithPlan.java

@@ -0,0 +1,42 @@
+/*
+ *  Copyright (c) 2016 Uber Technologies, Inc. (hoodie-dev-group@uber.com)
+ *
+ *  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.uber.hoodie.io.compact;
+
+import com.uber.hoodie.avro.model.HoodieCompactionPlan;
+
+/**
+ * Contains Hoodie Compaction instant along with workload
+ */
+public class HoodieCompactionInstantWithPlan {
+
+  private final String compactionInstantTime;
+  private final HoodieCompactionPlan compactionPlan;
+
+  public HoodieCompactionInstantWithPlan(String compactionInstantTime,
+      HoodieCompactionPlan compactionPlan) {
+    this.compactionInstantTime = compactionInstantTime;
+    this.compactionPlan = compactionPlan;
+  }
+
+  public String getCompactionInstantTime() {
+    return compactionInstantTime;
+  }
+
+  public HoodieCompactionPlan getCompactionPlan() {
+    return compactionPlan;
+  }
+}