Support log file Support .properties configuration, please check nacos-cpp-cli.properties for details

Major bug fix: Thread exit optimization, now the daemon thread will exit quickly, thus the client won't take much time to exit (compared with previous version) Special thanks to @wensheng-zhang for fixing bug in function getAllInstances (see #46 ) Service subscriber will now be displayed on nacos's panel. The client will now use both a poller and udp receiver to monitor the change of subscribed services, similar to Java client's implementation

Code polish: Constant headers' refactor