Add support for resources not sending the appropriate needed headers

[moagggi]

Some (misconfigured?!) servers do not send the Content-Length header. Given the current code it would not be possible to download from these sites. Additionally other servers do neither send Accept-Range nor allow Ranges. This would also fail downloads atm.

Given these two scenarios it would be good to have a fallback handler which downloads those files single threaded and unchunked - but downloads them.

[tahnik]

Yeah this definitely need to be added. Thanks