Add automatic p2p multi-nodes requests to spread the load on nodes

Duniterpy should handle multi-nodes requests to share the write load on nodes and to ensure to have the most valid information of the blockchain consensus.

Client should not care about how and where the requests are sent, and all the complexity should be in the library.

Then, all clients using Duniterpy, will be really p2p clients.

Sakia implementation : https://git.duniter.org/clients/python/sakia/blob/master/src/sakia/services/network.py#L250