[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>

wpilibcExamples/src/main/cpp/examples/ElevatorSimulation/cpp/Robot.cpp

@@ -88,7 +88,7 @@ class Robot : public frc::TimedRobot {
   void SimulationPeriodic() override {
     // In this method, we update our simulation of what our elevator is doing
     // First, we set our "inputs" (voltages)
-    m_elevatorSim.SetInput(Eigen::Vector<double, 1>{
+    m_elevatorSim.SetInput(frc::Vectord<1>{
         m_motor.Get() * frc::RobotController::GetInputVoltage()});
 
     // Next, we update it. The standard loop time is 20ms.