[Soc2014] Official meta API

This is a slightly weird "version changed"; yes, it's a change introduced in 1.8 but this API didn't formally exist in 1.7. It would be worth putting a note further up the page to note the fact that the _meta API existed in 1.7, but wasn't formally documented or supported; and down here, note that the many_to_many argument is part of the "old" API that is being supported to maximise backwards compatibility.