"Photo - pixiv" Extractor: Add support for ugoira's thumbnail

* Add requestAPI(), fixImageURLforUgoiraFromAPI()

FYI: http://www.pixiv.net/info.php?id=2476
     http://www.pixiv.net/member_illust.php?mode=medium&illust_id=44298467
"Photo - pixiv" Extractor: Fix coding style
"Photo - pixiv" Extractor: Fix fixImageExtensionFromAPI()