* 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
- Add support for all transaction types and ledger object types to gRPC
implementation of tx and account_tx.
- Create common handlers for tx and account_tx.
- Remove mutex and abort() from gRPC server. JobQueue is stopped before
gRPC server, with all coroutines executed to completion, so no need for
synchronization.
* update EP and find package requirements
* minor protobuf/libarchive build fixes
* change travis release builds to nounity to
ameliorate vm memory exhaustion.
FIXES: #3223, #3232
* use tagged containers for pkg build
* update build images
* continue to build container images in pipeline, but allow
failure (non-block)
* limit travis macos cache
* add vs2019 windows to travis
* remove xcode 9 travis build
* remove clang5/6 from CI and update min version of Clang required in
cmake
* break windows CI build into stages to reduce timeouts
* update datelib
* add if condition to travis builds to allow commit message to limit
builds by platform
