[HTTP] Call controller actions using URL from _publicApi instead of _query endpoint

[Shiranuit]

This PR depends on kuzzleio/kuzzle#2342
The tests will not pass until this PR (kuzzleio/kuzzle#2342) is merged and Kuzzle is released.

What does this PR do ?

This PR add the capability of calling controller's actions directly using their HTTP Endpoint instead of using the _query endpoint.
The SDK is going to try to fetch HTTP Endpoint from /_publicApi and build the routes to directly call the HTTP Endpoint.
If the SDK cannot fetch or build the routes from /_publicApi, it will fallback using the /_query endpoint

Other changes

Headers can now be added by adding a headers property in the request sent using query

HashMap<String, Object> request = new HashMap();
HashMap<String, Object> headers = new HashMap();

headers.put("foo", "bar");
headers.put("origin", baz");

request.put("headers", headers);

sdk.query(request);

Headers are returned in the Response object