nt2::value is not required anymore

As tests and other systems now rely on the Sequence or
FusionSequence nature of tested elements, the need for
the nt2::value extension point is moot. This patch removes
all reference to it.
make_unchecked_array_iterator is in <iterator>
Add unit test for UT safe_max
Fix MSVC2012 strange behavior in safe_max
dry behaves as a proper proxy
Fix ULP computation on non-fundamental types

Types like dry behave as their underlying value type but
don't get processed properly in max_ulps. This new strategy
consists to turn any unknown type into its primitive type
using .value() before computing ULP with fundamental type
formula.