- Support #487: Clean-up interface: for instance it is no longer required to define a method in Model to build the GodOfDof: Model is able to do it itself with just few tuples that indicate which objects in the input parameter file are related to a given god of dof. - Feature #478 - Design #202 - Support #233: FiniteEltSpace is now built from informations in the input parameter file. Unknowns handling has been strongly refactored in the process. - Feature #482: refactor domain, and build domain objects directly from informations in the input parameter file. A DomainManager and GeometricMeshManager have been introduced in the process. - Design #360: Review all uses of std::move and remove unrequired ones. - Feature #439: Reactivate Stokes model: replace one of the Dirichlet condition by an additional operator. Rename it more properly. - Support #470: Very minor changes in Elastic model.