* Reduce lock scope on all public functions
* Use TaskQueue to process shard finalization in separate thread
* Store shard last ledger hash and other info in backend
* Use temp SQLite DB versus control file when acquiring
* Remove boost serialization from cmake files
Switch to target-oriented dependencies. Use imported targets for
dependencies (openssl, boost). Localize FindBoost to remove cmake
version dependence for latest boost support. Logically separate
"ripple-libpp" core sources and add install targets.
Add ninja build for msvc. Add two clang sanitizer builds. Misc script
changes to work with latest modernized cmake.