File component upload directory, scheme, and extensions not loaded properly

File components currently do not load properly when editing an existing webform. Upon editing a file component, the extension list, file scheme (public/private), file size limit, and upload directory are all blank. Values seem to be saved properly if re-set, but after saving the webform and editing it again, all fields are blank again.

This problem appears to be caused by the fact that Webform does not set individual properties for all of these options. Rather than having properties like #filesize, #file_scheme, etc, there is a single property #upload_validators that needs to be parsed out into multiple settings. Likewise, the single #upload_location property needs to be split out into file scheme and directory. This patch addresses these problems with loading file components.