Moved reference resolution out of language-specific files; changed
things so that we parse the header args list in org-babel.el, and
changed the argument list of the org-babel-execute:LANG functions
accordingly. In addition to hopefully resulting in easier maintenance,
this results in more streamlined org-babel-execute:LANG functions, and
hence less work to do when adding interpreters.
When :results is 'value, the org-babel-LANG-evaluate functions are
responsible for returning an elisp representation of the *value* of
the block. This stage is maintained in the language-specific code
because different languages have different ways of doing it: python
and ruby use org-babel-LANG-table-or-string, whereas R and shell write
to file and then use org-babel-import-elisp-from-file. It could
however be put in the org-babel-execute:LANG function.
