Quality param

Hi,
I'm working on extend imageapi imagemagick support, but there is some problem on imagemagick command generated by this module. It's always append (after each action) a param for image quality (-quality 'XX'). I create a patch to add -quality param only if not already avaiable into other actions.

With this patch we can use im_raw (and extend imagecache_actions, ..) to put each param on end of command, like:

/usr/bin/convert input.png -xxx XXX -quality 'YY' -zzzz ZZZ output.png

for example to have support for image format you can use im_raw and add

-quality 'XX' jpg: >