Patch for JpegMeta.php

This patch allows a user to enter a datetime into the media editor
in what ever format they please, and yet still have it formatted
properly in the JPEG.  Strictly speaking, JpegMeta will store what
ever string you provide, but I'm guessing Google and other EXIF
readers may require the standard format.

darcs-hash:20050903125736-46f60-da93b57da8c2ce7ac5f5e1c24c195783b46730e5.gz