filter session types by terms

[stopfstedt]

refs #1725.

the SQL equivalent of this filter is

SELECT DISTINCT st.* 
FROM session_type st
JOIN session s ON s.session_type_id = st.session_type_id
LEFT JOIN session_x_term sxt ON sxt.session_id = s.session_id
LEFT JOIN term t ON t.term_id = sxt.term_id
LEFT JOIN course c ON c.course_id = s.course_id
LEFT JOIN course_x_term cxt ON cxt.course_id = c.course_id
LEFT JOIN term t2 ON t2.term_id = cxt.term_id
WHERE (
  t2.term_id IN (?) 
  OR t.term_id IN (?)
);