LPS-37434 Adding empty constructor to HttpPrincipal to support unmarshalling
LPS-37434 Adding new background task executor for remote staging
LPS-37434 Updating remote staging to use the background task executor
LPS-37434 Refactor BackgroundTaskContextMapFactory - extracting same parts from methods
LPS-37434 Add convenience method to provide a controlled way to exit from a background task
LPS-37434 The old way of reporting NO_LAYOUTS error won't work anymore due to the background task arrangement - refactoring the way we handle that error, and also cleaning up this error type, all export/import/staging processes are being transformed to background processes