Locking and dispatching performance improvements:

* Avoid taking the master lock in most peer operations
* Dispatch recvGetLedger to JobQueue
* Dispatch consensus ledger fetches.
* Release master lock earlier in RPCHandler
Ledger fetch improvements. Fetch policy improvements.
Refactor, tidy up:
* Fix for msvc std::function return types
* Convert macros to constants
* Add Journal to PeerSet and use in InboundLedger
* Break lines and add annotations
* Remove some warnings
OrderBookDB::addOrderBook cleanup
Make offerDelete and fill Items more robust.
Add ScopedPointer::reset
Improved human readable JSON-RPC error messages
Error reporting tests
Use duration in insight::Event, add chrono_util
Move PathRequests to separate files
Insight support for ResourceManager