Replace gamemode with separate settings

[thecraftianman]

Fulfills #243

• Removed the gamemode setting, competitive fuel settings, and everything directly related to them (ACF.Gamemode, ACF.CompFuelRate, ACF.CompFuelFactor)
• Added new serverside settings to enable/disable legality checks (ACF.LegalChecks) and enable/disable fuel requirements for engines (ACF.RequireFuel) to match Sandbox mode behavior
• Changed the default value of ACF.FuelRate to the Competitive mode value
• Added callback messages for every setting that didn't have one and fixed up the existing ones a bit because why not
• Very minor bits of style cleanup

I'm not sure if it would be ideal to keep the dropdown gamemode menu (to use as presets for the new settings) and/or a separate multiplier for the Competitive fuel consumption (as a checkbox probably?), but these can be added back if desired.

Radar behavior will also need to be changed to account for this PR (maybe moved to use the RestrictInfo setting instead or something? Done in TwistedTail/ACF-3-Missiles#88 )

[Stooberton]

Quality work 👍

Besides upping the default consumption to 27.8 I've got no issues with this.