(core) move home server into core

Summary: This moves enough server material into core to run a home server.  The data engine is not yet incorporated (though in manual testing it works when ported).

Test Plan: existing tests pass

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2552

app/common/DisposableWithEvents.ts

@@ -0,0 +1,28 @@
+/**
+ * A base class which combines grainjs Disposable with mixed-in backbone Events. It includes the
+ * backbone Events methods, and when disposed, stops backbone listeners started with listenTo().
+ */
+import {Events as BackboneEvents, EventsHash} from 'backbone';
+import {Disposable} from 'grainjs';
+
+// In Typescript, mixins are awkward. This follows the recommendation here
+// https://www.typescriptlang.org/docs/handbook/mixins.html
+export class DisposableWithEvents extends Disposable implements BackboneEvents {
+  public on: (eventName: string|EventsHash, callback?: (...args: any[]) => void, context?: any) => any;
+  public off: (eventName?: string, callback?: (...args: any[]) => void, context?: any) => any;
+  public trigger: (eventName: string, ...args: any[]) => any;
+  public bind: (eventName: string, callback: (...args: any[]) => void, context?: any) => any;
+  public unbind: (eventName?: string, callback?: (...args: any[]) => void, context?: any) => any;
+
+  public once: (events: string, callback: (...args: any[]) => void, context?: any) => any;
+  public listenTo: (object: any, events: string, callback: (...args: any[]) => void) => any;
+  public listenToOnce: (object: any, events: string, callback: (...args: any[]) => void) => any;
+  public stopListening: (object?: any, events?: string, callback?: (...args: any[]) => void) => any;
+
+  // DisposableWithEvents knows also how to stop any backbone listeners started with listenTo().
+  constructor() {
+    super();
+    this.onDispose(this.stopListening, this);
+  }
+}
+Object.assign(DisposableWithEvents.prototype, BackboneEvents);