[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>

wpimath/src/test/native/include/frc/system/RungeKuttaTimeVarying.h

@@ -6,7 +6,7 @@
 
 #include <array>
 
-#include "Eigen/Core"
+#include "frc/EigenCore.h"
 #include "units/time.h"
 
 namespace frc {