Don't refuse multipage images in CLI-based *Magick plugins
Properly display gif images
Added support for preview generation to *Magick media processing plugins.

This is useful for incoming files that contain multiple images, like
animates GIFs or multipage TIFFs.
Disable preview generation in Gmagick backend

Looks like the way you're supposed to traverse through multi-image
objects is not really working. writeimage always takes the first image
in the sequence, anyway.
Merge pull request #28 from collectiveaccess/multipage_tiff

Multipage tiff support