Dump all errors client side into a logfile, not just stdout

[AndyGrant]

Ciekce managed to have a case where crashes occurred in a game, but PGNs were not uploaded, even though the errors were reported to the server. This could happen in the case of a network disconnection during the final update at the end of the game. It could also have been a server error, which would have made its way back to the client and been noted. But without infinite stdout logging through nohup for example, the needed evidence was lost.