Add the FusionAssociativeSequence concept.
Add the Context concept.
Refactor @tparams in the doxygen comments.
Add mpl::is_subset and mpl::is_superset.
Remove ghost header: fwd/model/boost_variant.hpp.
Fix broken auto_struct.
Implement dyno::context (replaces detail::fusion_map).
Add the easy_map DSEL.
Add the Attribute concept and archetype.
Reword the Context concept and the extends intrinsic.
Refactor the Event concept and model.
Refactor the Framework concept and model.
Add dyno::detail::reordered_view.
Remove the Context concept.

It turns out that we can fusion::push_back in an associative
sequence, which makes part of `context` useless. The rest
of `context` is rendered useless by using a `reordered_view`.