Add support for the RPC server/client (request/reply) paradigms

[fabawi]

Add directories to Wrapyfi named "servers" and "clients" following the same convention as "publishers" and "listeners" containing all middleware. The request/reply paradigm should always wait: should_wait=True being always the case.

The equivalent of a server setting is activated by:

activate_communication(<Method name>, mode="reply")

The equivalent of a client setting is activated by:

activate_communication(<Method name>, mode="request")

The arguments are captured from the client (requester) and passed through to the server (replier), which returns the "reply" back to the server (itself) and the client.

Changes need to be made in the wrapyfi/connect/wrapper.py script to reflect new addition. Must initialize the server and client scanners in the init. Must carefully separate the publish/listen from reply/request

[fabawi]

The proposed paradigm corresponds to request/response on ZeroMQ, service client/server in ROS/ROS2, and YARP RPC client/server. At a later stage, we can consider adding the "should_wait=False" option which is analogous to client/server in ZeroMQ, action client/server in ROS/ROS2, and YARP (currently no asynchronous RPC client as discussed here