Extract general functions into utils

EKF/utils.hpp

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+#include <matrix/math.hpp>
+
+
+// converts Tait-Bryan 312 sequence of rotations from frame 1 to frame 2
+// to the corresponding rotation matrix that rotates from frame 2 to frame 1
+// rot312(0) - First rotation is a RH rotation about the Z axis (rad)
+// rot312(1) - Second rotation is a RH rotation about the X axis (rad)
+// rot312(2) - Third rotation is a RH rotation about the Y axis (rad)
+// See http://www.atacolorado.com/eulersequences.doc
+matrix::Dcmf taitBryan312ToRotMat(const matrix::Vector3f &rot312);
+
+// Use Kahan summation algorithm to get the sum of "sum_previous" and "input".
+// This function relies on the caller to be responsible for keeping a copy of
+// "accumulator" and passing this value at the next iteration.
+// Ref: https://en.wikipedia.org/wiki/Kahan_summation_algorithm
+float kahanSummation(float sum_previous, float input, float &accumulator);
+
+// calculate the inverse rotation matrix from a quaternion rotation
+// this produces the inverse rotation to that produced by the math library quaternion to Dcmf operator
+matrix::Dcmf quatToInverseRotMat(const matrix::Quatf &quat);