Core v5 upgrade

WIP

@johnsimons the main thing I haven't solved (see //todo for full list) is how to invoke the pipeline from our imports:

https://github.com/Particular/ServiceControl/commit/f2e9a4e9a8a963d9bd7041387bcfcf91090b36ab#diff-387918b610ebd403213008c724a79f64L57

Ideas?