XClass used along the application do not have coherent naming rules

The XClasses used by the mail archive do not have coherent names. They should be renamed for more clarity (and the Sheet and Template of course):

• mails : MailArchiveCode.MailClass
• topics : MailArchiveCode.MailTopicClass --> MailArchiveCode.TopicClass
• servers : MailArchiveCode.ServerSettingsClass --> MailArchiveCode.ServerClass
• lists : MailArchiveCode.ListsSettingsClass --> MailArchiveCode.ListClass
• types : MailArchiveCode.TypesSettingsClass --> MailArchiveCode.TypeClass
• matchers : MailArchiveCode.MailMatcherClass