Allow sparql-execute-query to return simple list from select

[johanwk]

The current sparql-execute-query always inserts query results into the current buffer. Could we have an option to return the results as a simple elisp list instead, so it can be bound to a variable, &c?

As a sketch: run the query with json result format in a temporary buffer (hopefully to handle multiline string values); apply json-parse-string to (buffer-string); transform into a simple list as return value.

The final RESULTS in the org-babel example below shows what I'd like to have directly from the query.

#+name: mysmall
#+begin_src sparql :url http://localhost:3030/bfo-core/query
select * {?x ?y ?z} limit 2
#+end_src

#+RESULTS:
| x              | y          | z                      |
|----------------+------------+------------------------|
| dc:contributor | rdf:type   | owl:AnnotationProperty |
| dc:contributor | rdfs:label | contributor            |

#+begin_src emacs-lisp :var result=mysmall() :results code :colnames no
result
#+end_src

#+RESULTS:
#+begin_src emacs-lisp
(("x" "y" "z")
 ("dc:contributor" "rdf:type" "owl:AnnotationProperty")
 ("dc:contributor" "rdfs:label" "contributor"))
#+end_src

PS. The main point here is to get the query results as a return value, rather than always inserted into the current buffer.