Support multiple references as single reference

[konard]

We should try to support multi-references:

(some example: some example is a link)

some example

And also we should switch to arrays for both id and values.

That means if we have defined any multi references in the file, it means we should treat some example in any places as single multi-reference.

So in that example we have multi-reference definition, and also multi-reference as a self reference for that link.

We need to try implement these feature in all supported languages, with the same set of tests.