IO::FlatDatastore::acquire_stream(): storage must be initialized only when reading.
IO::FlatDatastore: ensured boost::filesystem calls use error_code.
IO::FlatDatastore::acquire_stream(): create path to prop storage.
IO::FlatDatastore::release_stream(): assign storage prop state.
aux: added <memory> aliases.
Client::Unit::session_close(): added Cmd::Hive::StoreAll call.