Options Entrypoint 51bba4a

Since a GameSettings mixin is no longer needed to have Option instances properly registered, I propose adding an entrypoint so options are properly loaded without needing a mixin.

Usage:

public class ExampleMod implements OptionsInitEntrypoint {

    public static OptionBoolean exampleOption;

      . . .

    @Override
    public void initOptions(GameSettings gameSettings) {
        exampleOption = new OptionBoolean(gameSettings, "exampleOption", false);
    }
}

Fixes

• 8e2c760 Removed unused imports and made mixin classes abstract
• 06e200a Fixed PacketHandlerServerAccessor being registered as a common mixin (this would display a class load warning)