implement start, stop, unlock, unlockStop, readd debug, writedata never
calls enoughdata (causes lockup with sftp), seekable always returns
false (breaks sftp), fix return value on wrong offset if stream is not
seekable

* start - resets stream
* stop - calls enoughData and unlocks
* unlock - debug (technically this should call enoughdata)
* unlockStop - debug (technically this call kio->resume, but that is
done by needData)