Fix paths
I the recent work on the CreateDatabase task I assumed that DatabaseDocument.Id is the full document ID ("Raven/Databases/DatabaseName"). This assumption made the code to look nice, so instead of reverting those changes I think it is better to just made this supported. We now support DatabaseDocument.Id to be both the database name and the database ID.
When putting an index on a not exit database, we should return 503 rather then 404.