Move exec and events components to util module

The exec and events components are common components that
are used by both runtime and registry. It makes sense to
move them into the util package.

This also adds some docs to the registry module

packages/node_modules/@node-red/runtime/lib/index.js

@@ -20,19 +20,15 @@ var redNodes = require("./nodes");
 var flows = require("./flows");
 var storage = require("./storage");
 var library = require("./library");
-var events = require("./events");
 var hooks = require("./hooks");
 var settings = require("./settings");
-var exec = require("./exec");
 
 var express = require("express");
 var path = require('path');
 var fs = require("fs");
 var os = require("os");
 
-var redUtil = require("@node-red/util");
-var log = redUtil.log;
-var i18n = redUtil.i18n;
+const {log,i18n,events,exec,util} = require("@node-red/util");
 
 var runtimeMetricInterval = null;
 
@@ -65,7 +61,7 @@ var server;
  *                              better abstracted.
  * @memberof @node-red/runtime
  */
-function init(userSettings,httpServer,_adminApi,__util) {
+function init(userSettings,httpServer,_adminApi) {
     server = httpServer;
     userSettings.version = getVersion();
     settings.init(userSettings);
@@ -79,14 +75,6 @@ function init(userSettings,httpServer,_adminApi,__util) {
     redNodes.init(runtime);
     library.init(runtime);
     externalAPI.init(runtime);
-    exec.init(runtime);
-    if (__util) {
-        log = __util.log;
-        i18n = __util.i18n;
-    } else {
-        log = redUtil.log;
-        i18n = redUtil.i18n;
-    }
 }
 
 var version;
@@ -246,6 +234,10 @@ function reportMetrics() {
 
 /**
  * Stops the runtime.
+ *
+ * Once called, Node-RED should not be restarted until the Node.JS process is
+ * restarted.
+ *
  * @return {Promise} - resolves when the runtime is stopped.
  * @memberof @node-red/runtime
  */
@@ -266,17 +258,17 @@ function stop() {
 // This is the internal api
 var runtime = {
     version: getVersion,
-    get log() { return log },
-    get i18n() { return i18n },
+    log: log,
+    i18n: i18n,
+    events: events,
     settings: settings,
     storage: storage,
-    events: events,
     hooks: hooks,
     nodes: redNodes,
     flows: flows,
     library: library,
     exec: exec,
-    util: require("@node-red/util").util,
+    util: util,
     get adminApi() { return adminApi },
     get adminApp() { return adminApp },
     get nodeApp() { return nodeApp },