Many improvements to HTML5.

- Fixes to the Mac HTML5 Device selection. .app files now work correctly.
- Re-enabled HTML5 in Mac Editor.
- Added HTML5LaunchHelper executable to clean up the process of LaunchOn for HTML5.
- Improve HTML5 SDK Settings Editor interface. Only the emscripten install directory is needed now, SDK version are automatically picked up and selected for use.
- Change UnrealPak to also account for bytes saved (>64KB) and percentage size of original file (<90%) when choosing to automatically turn off compression.
- Added Server Port option for HTML5 deploy to stop clashes on port 8000
- Adding more logging for use during debugging & tracing.
- Added an option to turn on HTML5 tracing api and added calls to the api.
- Fix up check() macros to throw alert messages and be more clear that something has gone wrong on HTML5.

#codereview Ankit.Khare

[CL 2452979 by James Moran in Main branch]

Engine/Source/Developer/HTML5/HTML5TargetPlatform/Private/HTML5TargetPlatformModule.cpp

@@ -59,6 +59,11 @@ public:
 		}
 	}
 
+	virtual void GetInstalledSDKVersions(const TCHAR* SDKDirectory, TArray<FHTML5SDKVersionNumber>& OutSDKs)
+	{
+		FHTML5TargetPlatform::GetInstalledSDKVersions(SDKDirectory, OutSDKs);
+	}
+
 public:
 
 	// Begin IModuleInterface interface