Test build on win/vs2017-2019. Update findTBB to find oneTBB. Update tbb threads control (tbb::global_control) and loop (tbb::parallel_for_each) and mutex (std::mutex). Remove warnings.

Add Observer. Remove functions from python side and add as observer of Problem. Add loads directions as functions. Minor changes.

Add formulation classes to build set of equations, and remove build methods from Element (flow only).
Draft methods to compute freestream velocity.
Rework data structure of boundary.
Add const.
Improve test cases.

Refactor normal computation to remove duplicated code.

Limit pressure coef gradient for vacuum conditions. Raise tolerances to account for diff in mesh on diff machine. Rename variable to avoid keyword

New validated adjoint solver with gradients wrt to mesh and agnle of attack. Add mesh gradients computation in Element. Split run method in MshDeform. Minor changes.

Add automatic pin of a DOF if no Dirichlet BC is provided. Remove explicit Dirichlet, except in cylinder tests cases. Cleaning.