I'm not very happy with this, and I'm open to suggestions. I don't want to say "MetersPerSecondSquared" or even "MPSSq". Not only are they ugly, there are many possible units that could have that dimensionality, and so it feels wrong to say that m/s^2 is an acceleration. That said, UnitAccel is also ugly (especially with all of the prefixes). I'm not sure what a better plan is though.