Move the image files used in the media tests from includes/media to data/media as...

Move the image files used in the media tests from includes/media to data/media as the includes/media
was starting to get crowded with supporting image files.

This changes the following things
*Moves the media files to a different directory
*Changes the references to the files to reference there new locations

2 semi-unrelated changes
*Modify the README file that was basically giving credit for the images where due to explain what the images are for.
*set svn:mime-type to image/svg+xml for the svg files.