Fix NuGet/NuGetGallery#1922 by creating a job to generate search relevance rankings

Also added a simple in-process JobHost to replace 'nucmd work run'. (Yes, I'm a terrible person for putting this all in one commit. No, I won't split it up).
Added code to create destination container if it doesn't exist
Extended job lease for GenerateSearchRankings
Changed default storage account for search rankings to primary
Merge pull request #5 from NuGet/anurse/1922-relevancejob

Fix NuGet/NuGetGallery#1922 by creating a job to generate search relevance rankings