Incorporate new finite element methods in getfem++ 

Basically, It is sufficient to describe an element on the reference element, i.e. to describe each base function of each degree of freedom. Vectorial elements elements are partially supported ...(supported by the finite element kernel but none vector element is implemented for now).

To be done ... please read [] for more details and see the files getfem/getfem_fem.h, getfem/getfem_fem.cc for practical implementation.