eddie-communication: rework networking code to match CoAP standards

• new executable files for both client and server applications;
• resource publication: a node MUST provide a value for ep, d and base-address where the resources are located, while the payload of the request MUST contain a textual representation of the list of resources to publish; The resource directory will answer with a Location-Path, that can be used to modify the attributes of the publication;
• publication update: to update a previous publication, a node can perform a POST request using the Location-Path value obtained after the registration, to modify parameters of the publication; to remove a publication, a node can perform a DELETE request using the same Location-Path value obtained after the registration; to change the list of published resources, a node MUST perform a new publication;
• resource discovery: a node that wants to find resources in the network can reach the special resource /rd-lookup/res, specifying query parameters to filter the results.