#2 game numbers capped at 9999

[w0nderd0g]

The current design uses 4-digit game numbers.
Now that more than 10k games have been played, people
are having to recycle game numbers.

Should be able to support game numbers between 0000 and
999999, at least.

Use hierarchical subdirectory system so that no more
than 1k log files are in a given directory. (To avoid
thrashing dir system on some OSes.)