Add docs for THUMBNAIL_DEFAULT_OPTIONS
Add docs for THUMBNAIL_DEFAULT_OPTIONS

Mactory/easy-thumbnails,siovene/easy-thumbnails,jaddison/easy-thumbnails,emschorsch/easy-thumbnails,sandow-digital/easy-thumbnails-cropman,jrief/easy-thumbnails,emschorsch/easy-thumbnails,sandow-digital/easy-thumbnails-cropman,SmileyChris/easy-thumbnails,jrief/easy-thumbnails