Add on_server_startup event

Add startup event to the Clusterio module API which is raised at startup
of a Factorio server.  This is to server as a replacement for the
on_init and on_configuration_changed events which cannot be used in
modules.

Adds clusterio_patch_number global from the patcher in order to
implement this.  This is a number that's incremented every time the save
is patched.

lib/factorio/patch.js

@@ -65,6 +65,7 @@ function generateLoader(patchInfo) {
 	let lines = [
 		'-- Auto generated scenario module loader created by Clusterio',
 		'-- Modifications to this file will be lost when loaded in Clusterio',
+		`clusterio_patch_number = ${patchInfo.patch_number}`,
 		'',
 		'local event_handler = require("event_handler")',
 		'',
@@ -226,6 +227,9 @@ async function patch(savePath, modules) {
 		}
 	}
 
+	// Increment patch number
+	patchInfo["patch_number"] = (patchInfo["patch_number"] || 0) + 1;
+
 	// Remove any existing modules from the save
 	patchInfo["modules"] = [];
 	for (let file of root.file(/^modules\//)) {