Improve HTTP/1.1 byterange handling

Improve HTTP/1.1 byterange handling

Fix parsing of a Range: header to support:
 - multiple ranges (parsed, but not returned)
 - suffix byte ranges ("-2139")
 - correct handling of incorrectly formatted range headers
   (correct behaviour is to ignore the header and return the full
    file)
 - return appropriate error for ranges outside the file

Multiple ranges are parsed, but only the first range is returned.
Returning multiple ranges requires using the multipart/byterange
content type.