Add effective material model based on homogenization
To describe the response behavior of a (natural or manufactured) material, we use constitutive models. Analytical constitutive models, e.g. Hooke or Mooney-Rivlin, allow for computationally efficient material characterization. In many cases however, we are interested in the effective response of complex architected materials, metals... In such cases we often rely on an effective material model based on homogenization. There exist different homogenization strategies. The implementation should serve as general basis.