clean a mime header.
clean a mime header. This is a separate function, as many http libraries calculate it for the user
the value in an HTTP Accept or Content-Type header
the normalised mime string
given a mime header this normalises it to lower case and removes all extra white spaces
given a mime header this normalises it to lower case and removes all extra white spaces
a plain mime strong, eg: text/html
normalised (lowercased and without white spaces) version of the mime