data/pandoc.lua: split type and behavior tables

Clearly distinguish between a type and the behavioral properties of an instance
of that type. The behavior of a type (and all its subtypes) can now be amended
by adding methods to that types `behavior` object, without exposing the type
objects internals.

E.g.:

    pandoc.Inline.behavior.frob = function () print'42' end
    local str = pandoc.Str'hello'
    str.frob() -- outputs '42'

0 files changed, 0 insertions, 0 deletions