download_id support with better chunksize

Now we have chunksize same as block which make it little faster. all
downloads going to have an ID which will be used to stop etc. new
function for xbmc to play and tell the proxy when it stopped playing
which will remove the file and stop downloading.
calling mechanism,
		import proxy
		axelhelper =  proxy.ProxyHelper()
		axelhelper.playUrl(stream_url);