Fix infinite waiting after sync message sending or receiving failed.

Rename replaceable_unpacker to unpacker2, replaceable_udp_unpacker to udp_unpacker2, replaceable_packer to packer2,
 because their names confuse users, any packer or unpacker is replaceable for those packer or unpacker that has the same msg_type.

Return the concept of 'size' and 'empty' in class queue to the Container's, and introduce new concept 'size_in_byte' to represent the memory size occupied by the queue.

Make force_shutdown and graceful_shutdown be able to reconnect the server even if the link has broken.

Export some typedefs in container to class queue.

Optimize class queue.

Explicitly require the first parameter to be rvalue reference for i_packer::pack_msg(container_type&&, container_type&).