Json(b) extension

Hi all,

As you know, PostgreSQL introduced Json(b) support at the 9.4 version [1],
and hstore v2.0 saved in separate repository [2]. But although PostgreSQL
has this support at the core level, there are many useful functions, which
wasn't ported to Json(b) from hstore v2.0 and json. Here [3], I've made a
review of the missing Json(b) functions, which can be implemented. This
list can be updated in the future, of course. I want to implement the
missing functions in the form of extension (e.g. contrib/jsonx).

What do you think about this?

[1]: http://obartunov.livejournal.com/177247.html
[2]: http://www.sigaev.ru/git/gitweb.cgi?p=hstore.git;a=summary
[3]:
https://gist.githubusercontent.com/erthalion/10890778/raw/f042872a92a1ab22ed7eb753fee2358b60d99d4a/hstore_to_jsonb.rst