allow disabling alignement and vectorisation in Eigen
this helps with memory debugging using ddt
added a new feelpde directory to store solvers for particular pdes
start with fast marching solver for eikonal equation
add directory
@feelpp/rb4areo  added example using the fast marching solver to compute the distance function
to walls
that is useful for example for turbulence modeling (eg RANS models)
Merge branch 'feature/feells' into develop