Cannot execute a DELETE, PUT or POST request with an empty body

Let's say I need to perform a simple delete on a given path without sending any JSON data, calling NuxeoClient#delete(String url, String json) with json=null will always execute a GET request, see https://github.com/nuxeo/nuxeo-java-client/blob/master/nuxeo-java-client/src/main/java/org/nuxeo/client/api/NuxeoClient.java#L293

Workaround: pass "" as the json parameter.
Maybe we should provide an extra API: NuxeoClient#delete(String url)?

Same for PUT and POST, though I'm not sure if executing these methods with an empty body is a real use case.