Adding a new ImageMagickImageProcessor class to replace

Adding a new ImageMagickImageProcessor class to replace
the old JAIImageProcessor class. Removing the non-free JAI,
will bring us closer to making mir free. The new class uses
ImageMagick commandline programs who's path may be specified
in the config.properties configuration file.
I did a few other minor changes, like adding a ChangeLog file
and adding a few comments.