Implement native graphql support

[sweemeng]

Library exist at http://graphql.github.io/code/#python

We should support it because:-

• it simplify query to nested object, for example contact details and membership
• we do not need to do multiple http query for nested object
• it potentially reduce data size as we can query only field that we need
• it can limit query to nested object which save responses size
• it allow for custom query function easily instead of another python script.

Cons:-

• not REST compatible
• require rewrite, so we most probably have graphql endpoint run together with REST endpoint.