Use vanilla HTTP handlers (refactoring)

api/category.go

api/entry.go

api/feed.go

api/icon.go

api/payload.go

api/subscription.go

api/user.go

daemon/routes.go

fever/fever.go

http/context/context.go

http/handler/handler.go

http/handler/html_response.go

http/handler/response.go

http/handler/xml_response.go

http/request/request.go

http/response/html/html.go

http/response/json/json.go

http/response/response.go

http/response/xml/xml.go

locale/translations.go