allow to specify how many times we can try to connect to the database at startup

add config options:
db_startup_connection_max_attempts - default 0 (infinite)
db_startup_connection_attempt_delay - delay in seconds between attempts (default 5)

BREAKING CHANGE: WINIX_PLUGIN_INIT plugin message requires to set result status,
you have to set the result status to true (env.res) if your
plugin was initialized correctly, otherwise winix will not start

winixd/main/main.cpp

@@ -353,10 +353,6 @@ using Winix::app;
 	app.LogUserGroups();
 	Winix::SavePidFile(log);
 
-	// load plugins before loading sessions - session_manager.LoadSessions()
-	// because some of the plugins can init its own sessions dates
-	app.InitPlugins();
-
 	// app.Init() starts other threads as well (they will be waiting on the lock)
 	if( !app.Init() )
 	{