[Reviewer: Matt][From: Alex]Review for SAS logging infrastructure

Hi Matt, please can you review my changes to add SAS logging/correlation infrastructure to various components. 

I've not added a huge number of UTs. The function is mainly just plumbing where UT does not add much value. The same is true of testing individual events. However I have added UT for correlation on the HTTP interface. Let me know whether you think this is sufficient. 

Thanks,
Alex.