[wpimath] Add typedefs for common types

This makes complex code significantly easier to read.

frc::Vectord<Size> = Eigen::Vector<double, Size>
frc::Matrixd<Rows, Cols> = Eigen::Matrix<double, Rows, Cols>

wpilibc/src/main/native/cpp/simulation/DCMotorSim.cpp

@@ -42,5 +42,5 @@ units::ampere_t DCMotorSim::GetCurrentDraw() const {
 }
 
 void DCMotorSim::SetInputVoltage(units::volt_t voltage) {
-  SetInput(Eigen::Vector<double, 1>{voltage.value()});
+  SetInput(Vectord<1>{voltage.value()});
 }