Add server watchdog and config reload test
New config option: server.config_reload_interval_ms
New config option: 'debug.config'

Logs some information about configuration file loading and re-loading
Fix return value of mdp_send()
mdp_send() and mdp_recv() do not pass zero-length buffer in iovec
Improve "mdp_client.h" layout and comments
New "config sync" command