eic_data.yaml: static_casting constructors from double

To avoid narrowing warnings and errors which are fully anticipated by the choice of data model, we introduce here e.g.

        Vector2f(double aa, double bb)\n
          : a{static_cast<float>(aa)},b{static_cast<float>(bb)} {}\n

Other changes:

• initializer lists in constructors
• bugfix in Cov4f