Proper handling of filters with multiple values

This is a non-breaking functionality change -- previous documentation said you could specify multiple platform-slugs like

array('platform-slug' => 'partnerplayer', 'platform-slug' => 'bento')   

but that would silently fail, only returning the 'bento' stuff.

The corrected, and now functioning and documented, approach is

array('platform-slug' => array('partnerplayer', 'bento') )   

though single values can be strings

array('platform-slug' => 'partnerplayer' )