[MediaBundle] Use Imagick in all image filters

[FabianLiebl]

Some pictures use special color spaces, which leads to wrong colors in their formats after usage of our filters. This only seems to be the case when we use the default GD library, Imagick seems to not have that problem.
We already added a default usage of Imagick (if available) to ImageFilter.php and ImageBlurFilter.php, but we should also add it to BackgroundFilter.php and ImageZoomFilter.php.