Fix missing break on mtCLUSTER handler
Ledger fetch fixes.
Validate params before dispatching
Handle a removed peer when counting ledger use
Remove dead serializer signature code
New utility classes, containers, C++14 compatibility, and fixes:
* Add std::equal_to <void> (since C++14)
* Add heterogeneous std::equal (since C++14)
* Add maybe_const
* Add empty_base_optimization
* Add is_constructible specialization for pair, tuple
* Add aged associative containers:
  - aged_set, aged_map, aged_multiset, aged_multimap
  - aged_unordered_set, aged_unordered_map,
  - aged_unordered_multiset, aged_unordered_multimap
* Fix auto keyword pass by reference
* Fix basic_seconds_clock warning and project file
PeerFinder fixes:
* Fix split horizon using recent address cache
* Change message tuning parameters to reduce dead messages
* Improved peer handout algorithm for addresses
* Improved handout algorithm for redirects
* Improved selection algorithm for autoconnect
* Faster autoconnection strategy
* Consolidate deadline timers
* Send empty endpoints message as a socket ping
* Fix hop count adjustments for live cache filtering
* Remove broken Peer::isConnected function
* Optimized Livecache for handouts
* Optimized Bootcache for handouts
* Remove uptime metric from Bootcache entries
* Add histogram to Livecache print output