NanoMQ v0.7.8 更新日志

NanoMQ 0.7.8 changelog:

1. Add FoundationalDB as new data persistence option
2. Add a prototype of SQL parser engine
3. Add HTTP authentication webhook for verifying client connections
4. Optimize WebHook performance and success rate.
5. Use UNIX timestamp in online/offline event msg.
6. Add ZeroMQ proxy docs.
7. Backwards support for old GCC versions
8. Fix #603 #601 #600 #576 #566 #559