Header: Compose and send HTTP response headers

This class can be used to compose and send HTTP response headers.

It can add headers to the current HTTP request response for several purposes, such as redirecting the request to another URL, setting the content type or content disposition for downloads.

It can also set the response status and automatically determine the textual description by looking up a list of known response codes.

Once the list of headers is fully defined, the class issues the response header output commands.