Factory for state blocks

The factory will be able to create state blocks on the fly given:

• a key: string to identify the state block
• a Eigen::VectorXd with the state
• a bool with fixed/unfixed

Strings will be identified as follows:

• "O", a quaternion if Vector::size() == 4;
• "O", an angle if Vector::size() == 1;
• "O3", "Q", "Quaternion", "StateQuaternion": a state quaternion. The size must be 4.
• "O2", "A", "Angle", "StateAngle": a state angle. The size must be 1.
• "H3", "Homogeneous3D", a 3D homogeneous vector. The size must be 4.
• "P","V","I","W",... and many other letters: a regular SB. The size is that given by the provided Eigen::Vector.
• "Base", "Vector": a regular SB . The size is that given by the provided Eigen::Vector.

That is, any string other than "O, O3, Q, Quaternion, StateQuaternion, O2, A, Angle, StateAngle, H3 or Homogeneous3D" will produce a regular state block of the size indicated by the vector, and without local parametrization.

See that for orientations, the size is given as part of the string.