Added TweakScale_RealFuels and TweakScale_ModularFuelTanks

Hey! I decided I might as well help. This adds TweakScale_RealFuels and TweakScale_ModularFuelTanks to RealFuels.sln and ModularFuelTanks.sln, respectively.

I've not gotten an answer from @taniwha-qf about adding it to Modular Fuel Tanks yet, so I'm not 100% convinced I should add all this as one PR.