Define the public API properly

[mdumandag]

After merging #217, we will have some public methods that shouldn't be used by the users. (See #217 (comment)).

As written in the comment above, we could say that users should not use undocumented APIs. But this would require redesigning the structure of /docs folder. Right now, we are trying to document everything. IMHO, this is totally wrong, we should just list what should be public here.

Anyways, we could decide to go on a different direction to solve this. This issue is opened to track that before the 4.0 release.

[mdumandag]

Now, we properly display only the public API in the documentation and only expose the public parts to the user via HazelcastClient. Closing this issue now.