* canonicalize_replace_cache
* canonicalize_replace_client
Now it is clear at the call site that if there are
duplicate copies of the data between the cache and
the caller, which copy gets replaced.
Additionally data parameter is now const-correct.
If it is not going to be replaced (canonicalize_replace_cache),
then the shared_ptr to the client data is const.
* 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
