IO::FlatDatastore: corrected scope in already-FQN error messages.
Net::CmdStreamer: reworked read_stage() messages; added briefs for context IO.
Log: added report_error() overloads for std::exception, std::exception_ptr, and SerializerError.
aux: added std::deque and std::map specializations.
ConfigNode: added index property to built nodes.
Net::CmdStreamer: wrapped log messages in DUCT_GR_MSG_FQN().
Net::CmdStreamer::context_output(): wrapped serialization in try-catch and added error logging.