Small files can skew upload time statistics

[elonen]

In a small swarm, if a peer uploads a lot of small chunks, it will get unprortionally good upload time stats. Maybe change the statistics to bitrate instead (and calculate timeouts from there) to avoid this?

[elonen]

Slow downloaders can still skew it, but it's one less error source.

[elonen]

Alternatively (to using bandwidth as score), fileio.upload_chunk() could always normalize upload times as if upload had been of max chunk_size.