Better structure for upgrade doc

docs/unreal_upgrade.md

@@ -1,26 +1,33 @@
 
 # Upgrading Unreal Engine Version
 
-If you are using old version of AirSim with Unreal Engine 4.15 or earlier, here are some notes. More complete details are at [Unreal forum post](https://forums.unrealengine.com/showthread.php?145757-C-4-16-Transition-Guide).
+## Blocks Project
 
-**Note:** If you are using Blocks project that comes with AirSim then you don't need to do anything other than [installling Unreal 4.16](build.md).
+If you are using Blocks project that comes with AirSim then you don't need to do anything other than [installling Unreal 4.16](build.md).
 
-If you have your own Unreal project using AirSim plugin then you need to upgrade your project to use Unreal 4.16. If your project doesn't have any code or assets other than environment you downloaded then you can also simply [recreate the project in Unreal 4.16 Editor](unreal_custenv.md) and then copy Plugins folder from `AirSim/Unreal/Plugins`. Alternativly, follow below instructions.
+## Your Own Unreal Project
+If you have your own Unreal project using AirSim plugin then you need to upgrade your project to use Unreal 4.16. 
+
+### Option 1: Just Recreate Project
+
+If your project doesn't have any code or assets other than environment you downloaded then you can also simply [recreate the project in Unreal 4.16 Editor](unreal_custenv.md) and then copy Plugins folder from `AirSim/Unreal/Plugins`. 
+
+### Option 2: Modify Few Files
 
 Unreal 4.16 Build system has breaking changes. So you need to modify your *.Build.cs and *.Target.cs which you can find in `Source` folder of your Unreal project. So what are those changes? Below is the gist of it but you should really refer to [Unreal's official 4.16 transition post](https://forums.unrealengine.com/showthread.php?145757-C-4-16-Transition-Guide).
 
-### In your project's *.Target.cs
+#### In your project's *.Target.cs
 1. Change the contructor from, `public MyProjectTarget(TargetInfo Target)` to `public MyProjectTarget(TargetInfo Target) : base(Target)`
 
 2. Remove `SetupBinaries` method if you have one and instead add following line in contructor above: `ExtraModuleNames.AddRange(new string[] { "MyProject" });`
 
-### In your project's *.Build.cs
+#### In your project's *.Build.cs
 Change the constructor from `public MyProject(TargetInfo Target)` to `public MyProject(ReadOnlyTargetRules Target) : base(Target)`.
 
-### In your *.uproject
+#### In your *.uproject
 Remove line for `EngineAssociation`
 
-### And finally...
+#### And finally...
 1. Make sure [Unreal 4.16 is installed](build,md).
 2. Double click on your project's `*.uproject` file.
 3. If you are asked to select Unreal version, select 4.16.