Add constexpr core::get<T> functions for use with std::pair<T, U>
Add pointer typedef to function_traits
Fix possible ambiguity with functional component's invoke

Small style fix for any's internals
Remove logic from bad_optional_access. It now inherits its constructors.
Fix issue with invoke and constexpr

I should pay more attention to what can and cannot be constexpr in
C++11. std::forward<T> is *not* constexpr and therefore my logic breaks
down in these cases.

I can always add the features for unpacking and runpacking to be
constexpr in c++14 which will be the v2 namespace for this library.
Fix potential memory leak with std::exception_ptr in expected<T>
Remove constexpr core::get<T> for std::pair (see previous notes about constexpr)
Add value_at and type_at to utility component based on proposal N3761

Add comment on which proposal core::invoke comes from