Add server and host columns to data_imports to fix #1278

This adds 'server' and 'host' data to DataImport, so you can display that information without parsing. Old imports will have that column empty, but a person who is debugging can take a look at the log if he want.
why do we need to pass the server if it was using Socket.gethostname? apart from that, is it a good idea to let the job producer to fill in information about where that will be executed?