Add staffrole item image, rake config
Revert init.db, change item staffroll to credits

Revert init.db to same with dropItem.yaml.
Change item description staffroll to credits, and change Rakefile.
Change credit description of font, with adding font author
Merge pull request #24 from ichiko/staff_role

スタッフロールの画像を追加して、Rakefileの生成処理を変更した