Create Thumbnails Using ImageMagick

This code uses ImageMagick and Ghostscript to generate DSpace thumbnails of higher quality than the out-of-the-box capability of DSpace. Ghostscript allows DSpace's media filter to generate thumbnails from PDF bitstreams (similar to the XPDF method mentioned in the DSpace Manual, but with higher quality).

### Installation Dependencies
This solution requires ImageMagick and Ghostscript to be installed on the server where DSpace is running.  Each of these utilities must exist in DSpace's runtime path.  These applications will be run from the command line.

### Build Dependencies
This solution adds a build dependency on [im4java](http://sourceforge.net/projects/im4java/)

### Configuration

**Changes needed in DSpace configuration file, `dspace.cfg`:**

    plugin.named.org.dspace.app.mediafilter.FormatFilter = \
        org.dspace.app.mediafilter.LitImageThumbnailFilter = LIT Image Thumbnail, \
        org.dspace.app.mediafilter.LitPdfThumbnailFilter = LIT PDF Thumbnail, \

    filter.org.dspace.app.mediafilter.LitImageThumbnailFilter.inputFormats = BMP, GIF, image/png, JPG, TIFF, JPEG, JPEG 2000
    filter.org.dspace.app.mediafilter.LitPdfThumbnailFilter.inputFormats = Adobe PDF

    # GU ImageMagick Customizations
    org.dspace.app.mediafilter.LitImageMagickThumbnailFilter.ProcessStarter = /usr/bin
    org.dspace.app.mediafilter.LitImageMagickThumbnailFilter.ThumbnailWidth = 180
    org.dspace.app.mediafilter.LitImageMagickThumbnailFilter.ThumbnailHeight = 120