Non destructive state reconciliation

[Deleranax]

Implement non destructive state reconciliation protocol (merging two non conflicting states, i.e. that doesn't contain mutation about the same file).

[Deleranax]

The reconciliation must protocol must detect if at least on of the peers have the writing capability to undergo reconciliation. If none have it, the peers must "blacklist" each other and attempt another synchronisation with an other peer. When they successfully synchronise (or receive a change/reconciliation notification that matches their state), the peer is un-blacklisted.