Break out actions and payloads to their own files

The definitions take up a lot of space which makes it hard to see the dispatcher class, so break them out.

src/dispatcher/dispatcher.ts

@@ -17,55 +17,8 @@ limitations under the License.
 */
 
 import { Dispatcher } from "flux";
-
-export enum Action {
-    // TODO: Populate with actual actions
-}
-
-// Dispatcher actions also extend into any arbitrary string, so support that.
-export type DispatcherAction = Action | string;
-
-/**
- * The base dispatch type exposed by our dispatcher.
- */
-export interface ActionPayload {
-    [property: string]: any; // effectively makes this 'extends Object'
-    action: DispatcherAction;
-}
-
-/**
- * The function the dispatcher calls when ready for an AsyncActionPayload. The
- * single argument is used to start a dispatch. First the dispatcher calls the
- * outer function, then when the called function is ready it calls the cb
- * function to issue the dispatch. It may call the callback repeatedly if needed.
- */
-export type AsyncActionFn = (cb: (action: ActionPayload) => void) => void;
-
-/**
- * An async version of ActionPayload
- */
-export class AsyncActionPayload implements ActionPayload {
-    /**
-     * The function the dispatcher should call.
-     */
-    public readonly fn: AsyncActionFn;
-
-    /**
-     * @deprecated Not used on AsyncActionPayload.
-     */
-    public get action(): DispatcherAction {
-        return "NOT_USED";
-    }
-
-    /**
-     * Create a new AsyncActionPayload with the given ready function.
-     * @param {AsyncActionFn} readyFn The function to be called when the
-     * dispatcher is ready.
-     */
-    public constructor(readyFn: AsyncActionFn) {
-        this.fn = readyFn;
-    }
-}
+import { Action } from "./actions";
+import { ActionPayload, AsyncActionPayload } from "./payloads";
 
 /**
  * A dispatcher for ActionPayloads (the default within the SDK).