This removes mappintracker and sets stateless tracker as the default (and only) pintracker component.
Because the stateless tracker matches the cluster state with only ongoing operations being kept on memory, and additional information provided by ipfs-pin-ls, syncing operations are not necessary. Therefore the Sync/SyncAll operations are removed cluster-wide.
I cannot have RPCAPIs expose a SvcID() method as gorpc will warn about it not
having the right signature. So I have created an RPCServiceID() method instead.