Added 20 sets to [DGC] Collection

Previews & DDL:

	[DGC] 2007.12 No.521 Nao Matsuzaka 松坂菜央
	[DGC] 2007.12 No.522 Nodoka Ayukawa 鮎川のどか
	[DGC] 2007.12 No.523 Airi Hirose 広瀬愛梨
	[DGC] 2007.12 No.524 Aimi Hoshii 星井愛美
	[DGC] 2007.12 No.525 Koharu Morino 森野小春
	[DGC] 2007.12 No.526 Sena Akikawa 秋川せな
	[DGC] 2008.01 No.527 Aya Beppu 別府彩
	[DGC] 2008.01 No.528 Akina Minami 南明奈
	[DGC] 2008.01 No.529 Shizuka Nakamura 中村静香
	[DGC] 2008.01 No.530 Sheena Akane シーナ茜
	[DGC] 2008.01 No.531 Hikaru Wakana 若菜ひかる
	[DGC] 2008.01 No.532 Mai Hagiwara 萩原舞
	[DGC] 2008.01 No.533 Kei Kurokawa 黒川ケイ
	[DGC] 2008.01 No.534 Erika Kurosaki 黒崎えりか
	[DGC] 2008.01 No.535 Ai Nanase 七瀬愛
	[DGC] 2008.01 No.536 Yuki Nakayama 中山幸
	[DGC] 2008.01 No.537 Hisato Hayashi 林ひさと
	[DGC] 2008.01 No.538 Mika Matsushima 松島未果
	[DGC] 2008.02 No.539 Aki Hoshino ほしのあき
	[DGC] 2008.02 No.540 Yu Akiyama 秋山優