Automatically shut down if it failed to start properly

[bertfrees]

This is already the case if the web service was able to start but there is something wrong with authentication. However when the web service bundle is not started at all for some reason the program just keeps running. We should be able to detect this state and shut down. Similarly, if the Pipeline is started in GUI mode and the GUI bundle fails to start, the program should shut down.

This idea could be extended to check for the correct start of any number of specified bundles or services (idea also touched here).

Related is the "healthcheck" idea for the Docker build: #140 (comment). This is only useful for the Docker build though.

[bertfrees]

This is now done for the GUI: a splash screen (#149) is displayed while the required services start up, and the program shuts down after a certain timeout. At the moment the error message is not very useful though (just a generic error).