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/plugins/ticket/init.cpp

@@ -130,6 +130,7 @@ void RemoveTicket(PluginInfo & info)
 void InitTicket(PluginInfo & info)
 {
 	ticket_info.progress_prefix = info.config->Text(L"ticket_form_progress_prefix", L"progress");
+	info.res = true;
 }