Mnorm

mnorn and globalnorm have been writen to compute respectively matricial and vectorial norms  with dynamic or static choice of the formula used.

norm which mimicks the matlab behaviour calls these two accordingly, but is no more called directly by any
nt2 functor.

Definition and mode of choice of the norms can be seen in dox tables situated in globalnorm.hpp mnorm.hpp and norm.hpp
in fact do we even need them to be as_<> ? We never hierarchize on target_<> but we use unspecified.