linux/communication: move resource directory object into EddieEndpoint

• move resource directory object into EddieEndpoint, including methods that use the resource directory (ip/port getters, discover_rd, publish/unpublish)
• access the resource directory using only coap requests even if the resource directory is local, without having to use direct method calls when the rd is in the same node.
• remove remove_endpoint and add_endpoint from ResourceDirectory because not necessary anymore
• move endpoints_to_string_list_filtered and rd_resources_to_string_list_filtered into private in ResourceDirectory
• adapt tests, eddie-endpoint, VirtualizationReceiver to the new changes

Signed-off-by: Francesco Pham francesco.pham@huawei.com