Fix for issue # 1804 (Opened by me) (#2278)

Code Summary.md

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+
+## Code Summary Information ##
+_The summary file provides a simple way to navigate through the source code to understand the architecture of the application. It follows the below principles:_
+
+* **Word** highlighted in **bold** are **java class** files within the source code
+* The relative path of these **java class** files can be found in the attached _**csv**_ file
+* _**Word**_ highlighted in both _**bold**_ and _**italic**_ are _**standard java class**_ files
+
+#### IoTDB ####
+The entry point for the server is **[IoTDB](https://github.com/apache/iotdb/tree/master/server/src/main/java/org/apache/iotdb/db/service/IoTDB.java)**. It performs following tasks during the setup
+
+* It calls **StartupChecks** and performs the following check
+  * Checks JDK Version if it is greater than 8
+  * Checks JMX Port
+Next, it performs following activities and registers the essential services:
+
+* Adds **IoTDBShutdownHook** to the _**Runtime**_
+* Adds new instance of **IoTDBDefaultThreadExceptionHandler** into _**Thread**_
+* Uses **RegisterManager** to register following services
+  * **JMXService**
+  * **FlushManager**
+  * **MultiFileLogNodeManager**
+  * **Monitor**
+  * **StatMonitor**
+  * **Measurement**
+  * **ManageDynamicParameters**
+  * **TVListAllocator**
+  * **CacheHitRatioMonitor**
+  * **StorageEngine**
+  * **RPCService**
+  * **MetricsService**
+  * **MQTTService**
+  * **SyncServerManager**
+  * **UpgradeSevice**
+  * **MergeManager**
+  * **HotCompactionMergeTaskPoolManager**
+
+#### IoTDB Cli ####
+The entry point for the IoTDB Cli is **[Cli](https://github.com/apache/iotdb/blob/master/cli/src/main/java/org/apache/iotdb/cli/Cli.java)**.