Work on doc
gf : clean product mesh

- reinterpret array is much simple.
clean old code after check on various compilers
arrays : clean move constructor of cuboid::map

- remove mess linked to old icc 13 support
and write a clear and readable code.
arrays : revised version of map & fold

- also cleaned a bit reinterpretview example
arrays : fix in bug in ref counting in deserialize
Fix matrix * alias issue and adapt det_manip

- The previous version of the * operator for matrix was too clever.
It was giving a lazy object and then rewriting C = A *B into gemm (a,A,B,0,C).
The pb was in case of aliasing : when e.g. C = A, or is a part of A.
gemm is not correct that case, and as a result generic code like
a = a *b
may not be correct in matrix case, which is unacceptable.

- So we revert to a simple * operator for matrix
that does immediate computation.
Same thing for matrix* vector

- we also suppress a_x_ty class.

-> for M = a * b,
when M is a matrix, there is no overhead due to move assignment
-> however, when M is a view, there is an additionnal copy.

-Correctness comes first, hence the fix.
However, if one wants more speed and one can guarantee that
there is no aliasing possible, then one has to write a direct gemm call.

-> det_manip class was adapted, since in that case, we can show there
no alias, and we want the speed gain, so the * ops where replaced
by direct blas call (using the array blas interface).

-> also gemm, gemv, ger were overloaded in the case the return
matrix/vector (i.e. last parameter of the function) is not an lvalue,
but a temporary view created on the fly.
add c14 details in std::c14

- to use already a few c14 convenience details :

-> polymorphic std::plus, e.g.
   boost::mpi::reduce (world, A,C, std::c14::plus<>(),0);
this plus determine the type by itself ...
  -> errors on the type can be very cryptic on the gf.

-> add std::c14::make_unique
(equivalent of make_shared for unique_ptr).
gf: minor correction for 2 times, etc...

-> are going to be replaced soon anyway ...