Unified SpecialObject and NativeObject.  Fixed up shape tree type system to be more reasonable.
Added weak value constructors.
Added [u]int[64|32] casting helpers.
Changed Value implementation to be more robust.  Changed shape tree design.
Moved value implementation into value.cpp and value_inlines.hpp
Split rooting code into rooting.cpp and rooting_inlines.hpp
Split runtime implementation into .cpp aind _inlines.hpp file.