In the 'TOSCA Artifacts' view for a service, add a download icon (similar style to the existing upload icon) to the 'Tosca Model' row in the table.

When clicked a window shall be opened to allow the user select a csar from the file system and once selected, it shall be invoked to update the service.

If an error occurs a clear and explicit error message shall be presented to the user

It shall only be possible to upload when the service is checked out