Externalize the extra rules

[kevinlul]

The handling is very hardcoded in the game client. We can add an array field to a config JSON listing their corresponding rule card and excludes. A special case needs to be made for Speed Duels since that has its own handling.

Whether sysstrings are mapped in a contiguous range or individually in this config is a matter of taste. Same for whether the bits are implicit by their position in the config array or explicitly a field is also a matter of taste. Keep in mind that with the current protocol, only 16 options are available.

This should probably not be in configs.json but be in a separate file like the lflists, synced to canonical Git repositories so they stay the same on servers (paramount to network protocol) and allow flexibility if we change rule passcodes or alter the offered rules.

[kevinlul]

Some duel modes may need to be loaded as pure scripts instead of fake cards.

[kevinlul]

Additionally, Speed Duel, Rush Duel, and similar may be blended into the Duel Rule dropdown rather than as an extra rule, but this would change server implementations too.