Add std::make_unique
Refactor KeyCache
Use abstract_clock
Tidy up for C++11, and fixes:
* Remove shared_ptr legacy support
* Add make_unique support for pre-C++14 environments
* Fix comparison bug in sqdb
* Use std::shared_ptr in a few places
Fix and tidy up NodeStore
* Use std::unique_ptr
* Move globals to Manager singleton (fixes RocksDB exit crash)