Tuning and cleanups for ledger fetching

* Track stats for ledger fetch and output
* Reduce entries queried on timeout
* Allow duplicate node requests on timeout
* Don't query deep on timeout
* Adjust latency tuning
* Change high latency cutoff
* Set absolute limit on reply entries
* Small optimizations

src/ripple/app/ledger/impl/InboundLedgers.cpp

@@ -144,7 +144,6 @@ public:
     */
     // means "We got some data from an inbound ledger"
 
-    // VFALCO TODO Why is hash passed by value?
     // VFALCO TODO Remove the dependency on the Peer object.
     /** We received a TMLedgerData from a peer.
     */