Clean up FemElem2D::computeShapeFunctionsParameter

Clean bad loops and unnecessary temporary variable double x[3], y[3].
Reduced evaluation to non-null parts only, take into account that x0=y0=y1=0
Clean transformation from global 3D to triangle 2D local coordinates

Use the RigidTransform3d to apply the transformation inverse.
Much cleaner than accessing the m_R0 3x3 block all the time, and doing the rigid transformation by hand (removing the translation part and apply the rotation).
Renaming methods to follow coding standard in FemElem2D
FemElem2D test against epsilon + typo + compare double variable against 0.0
Store membrane shape functions (3 x 3param) in a 3x3 matrix
FemElem2D: rename m_R0 in m_initialRotation + make it a 3x3 matrix (not 18x18)
FemElem2D: clean up member variables that can be locally defined

    Matrix36Type m_membraneStrainDisplacement; //< Strain-displacement matrix containing (dfi/dx=bi , dfi/dy=ci)
    Matrix33Type m_membraneEm; //< Membrane elasticity material matrix
    Matrix66Type m_membraneKLocal; //< Membrane local stiffness matrix

    std::array<Matrix39Type, 3> m_plateStrainDisplacementAtGaussPoints; //< Strain-displacement at given Gauss points
    Matrix33Type m_plateEm; //< Membrane elasticity material matrix
    Matrix99Type m_plateKLocal; //< Membrane local stiffness matrix