Rename `sourcefile` and `sourceline` to `file` and `line`

    The resource endpoint was using the terms `sourceline` and
    `sourcefile` to reference the manifests; other places in
    the API were simply referring to these as `line` and `file`.
    
    This commit changes the names to be consistent (`line`, `file`)
    for v3, while ensuring that the old names still work properly
    on the older versions of the query API.