This patch improves Japanese translation for field_attr_* which are used in LDAP configuration page.

• Fix UI inconsistency: Japanese translation for "Login", "First name", "Last name" and "Email" in Redmine are "ログインID", "名", "姓", "メールアドレス". But different words ("ログイン", "名前", "苗字"　and "メール") are used in field_attr_*.
• Improve understandability: The current translations, "ログイン属性", "名前属性", "苗字属性" and "メール属性", are look like one word. In order to resolve this problem by indicates that they are two words, the patch insert a particle "の":https://en.wikipedia.org/wiki/Japanese_particles#no between words ("名属性" -> "名の属性").