Modified file include accordingly

 - Revert default value of span. - Removed api test for 3D because it could lead to issues when ctests run in parallel (tests would open the same files at the same time which would cause high latency. - Fixed values of Rae 3D case wrt to previous fix

Plus fixed a bug that would set span to 0

Refactor api + updated tests with mode updater and added scalers

API only works for 2D cases

+ Refactor adjoint and api's

The api features 3 components: The solver, the geometry and the initial mesh. The api is tested in a aerodynamic shape case where the NACA0012 is constrained at 0deg AoA with cl=0.40 and the objective function to minimize is the drag wrt the max camber and the max camber position. The test case ends with a final shape close to the NACA4412 (camber = 35% & max camber pos = 41%)

Fixed API, dart interface and prevented segfault if the number of sections is not imposed correctly.

Contains 2D and 3D developements as well as the api.