Major updates to most network classes.
Simplify CNetServer so it doesn't duplicate any client behaviour; all
players now run CNetClient.
Remove most player/slot management from networking code.
Wait for all players to finish loading before starting the simulation.
Remove CGameAttributes; attributes are now just a JS object.
Remove CPlayer; they are now just simulation entities.
Handle player colours via simulation system.
Add a default map for Atlas, so it always has something to load.
Move network documentation to Doxygen.
Remove lots of now-unused code.
This was SVN commit r7653.
