Updating dm_fileio

It is desireable that dm_fileio is updated by as few people as possible assuring that these updates are compatible with the rest of the file format utility routines and the IDL versions. I suggest that, in case of doubt, any requested add-ons are sent to Jan Steinbrener, who will try to implement them in a timely manner. Additionally there is a textfile called dm_fileio_changelog where any changes should be documented in detail and don't forget to add your initials in case I need to get back to you about it.