Baseviews

inspired by http://wagn.org/view_type_labeled_fails_to_convert_properly

pr adds support for open, closed, and labeled in the base format class; none of these were supported before, leading to breakage from explicit views in inclusions in non-html formats.

also re-arranged define_view and alias_view a bit to make it so that you can now define an unknown view via aliasing (not previously possible).  This is especially key in the base class.