Backports of new features and fixes from Jsonata reference

Relevant changes since 2.0.6:

https://github.com/jsonata-js/jsonata/commit/9e1523daa6c170320a3a55185ff77fb0df62f031

https://github.com/jsonata-js/jsonata/commit/09dba374ce9475e5fb08eee4d99de59bd72a2c8b
