Simultaneously fix a bunch of memory leaks in DaZeus.

* ConfigReader: when destroying a NetworkConfig, also destroy its ServerConfigs
* ConfigReader: destroy all SocketConfigs, all PluginConfigs and the GlobalConfig
* DaZeus: free the database handle
* PluginComm: after parsing a JSON message and sending a response, release them
* PluginComm: after sending a delayed command, release it