More helpful error message when react-native start is forgotten

Summary:
Developing with react-native on Linux, I found myself facing this message:

![chpao3jwuaehr_p jpg large](https://cloud.githubusercontent.com/assets/1598317/15032665/ae90ee88-1263-11e6-9acd-3fe261c08c28.jpeg)

The problem is actually quite simple: I hadn't used `react-native start` before starting `react-native run-android`, which caused this error, both on an emulator and a real Android device. As the message is currently unhelpful, but can be shown because of a simple mistake, I updated it.

~~Additionally, I clarified the fact that `react-native start` is still necessary on Linux, updating a title on the Linux and Windows Support documentation page.~~
Closes https://github.com/facebook/react-native/pull/7396

Differential Revision: D3305078

fbshipit-source-id: 2d87e02ff2ad15d8239fbcc0ada4a4e67b982e94

ReactAndroid/src/main/jni/react/JSCExecutor.cpp

@@ -277,9 +277,12 @@ void JSCExecutor::flush() {
 
   if (!ensureBatchedBridgeObject()) {
     throwJSExecutionException(
-        "Couldn't get the native call queue: bridge configuration isn't available. This "
-        "probably indicates there was an issue loading the JS bundle, e.g. it wasn't packaged "
-        "into the app or was malformed. Check your logs (`adb logcat`) for more information.");
+      "Could not connect to development server.\n"
+      "Try the following to fix the issue:\n"
+      "Ensure that the packager server is running\n"
+      "Ensure that your device/emulator is connected to your machine and has USB debugging enabled - run 'adb devices' to see a list of connected devices\n"
+      "If you're on a physical device connected to the same machine, run 'adb reverse tcp:8081 tcp:8081' to forward requests from your device\n"
+      "If your device is on the same Wi-Fi network, set 'Debug server host & port for device' in 'Dev settings' to your machine's IP address and the port of the local dev server - e.g. 10.0.1.1:8081");
   }
 
   std::string calls = m_flushedQueueObj->callAsFunction().toJSONString();