The "satellite fetch-pieces" command allows a satellite operator to
fetch as many pieces of a segment as possible, along with their
original order limits and hashes as provided by the storage nodes. The
fetched pieces and associated info will be stored on in a specified
folder as they are, rather than being RS-decoded or decrypted.
It is hoped that this will allow easier debugging of certain one-off
problems we've observed in the wild.
Change-Id: I42ae0e9ef0023538e42473a9be5a2460a3ac0f3a
