TIKA-1170: Insufficiently specific magic for binary image/cgm files
   - Applied patch from Andrew Jackson which…
   - Added additional matches to image/cgm magic
   - Added example cgm file
   - Added test of image/cgm to MimeDetectionTest


git-svn-id: https://svn.apache.org/repos/asf/tika/trunk@1519664 13f79535-47bb-0310-9956-ffa450edef68