feat: move all the source code to app folder

Till now `nativescript-dev-webpack` plugin requires automatically all (root|page)(.css|.xml|.js|.ts) files from the unit-test-runner. However, this behavior was changed and now `nativescript-dev-webpack` plugin requires automatically all files except the files from App_Resources and .d.ts files. This led to the problem that `preuninstall.js` and `postinstall.js` scripts are automatically required. These scripts require `nativescript-hook`. On the other side `nativescript-hook` has a dynamic require here https://github.com/NativeScript/nativescript-hook/blob/master/index.js#L56. As this dynamic require is not compatible with webpack's concept for dynamic requires, the following warning is shown:
```
WARNING in ../node_modules/nativescript-hook/index.js 56:27-51
Critical dependency: the request of a dependency is an expression
 @ ../node_modules/nativescript-unit-test-runner/postinstall.js
 @ ../node_modules/nativescript-unit-test-runner sync (?<!App_Resources.*).(xml|css|js|(?<!d.)ts|scss)$
 @ ./app.js
```

This PR moves all the app's related code to the app folder. This way `nativescript-dev-webpack` will require automatically all files from app folder and the unneeded files (as postinstall and preuninstall) will not be required.

Author: Fatme

app-root.xml renamed to app/app-root.xml

@@ -1,4 +1,4 @@
-/// <reference path="./declarations.d.ts"/>
+/// <reference path="../declarations.d.ts"/>
 import { Observable } from "tns-core-modules/data/observable";
 import { ObservableArray } from "tns-core-modules/data/observable-array";
 import * as http from "tns-core-modules/http";
@@ -21,7 +21,7 @@ function enableSocketIoDebugging() {
     global.window = global;
 }
 
-var config: INetworkConfiguration = require('./config');
+var config: INetworkConfiguration = require('../config');
 config.options = config.options || {};
 if (!config.options.appDirectoryRelativePath) {
     config.options.appDirectoryRelativePath = "app";
@@ -207,7 +207,7 @@ export class TestBrokerViewModel extends Observable {
         };
 
         this.updateView({ serverInfo: `connecting to ${this.baseUrl}`});
-        let io = require('./socket.io');
+        let io = require('../socket.io');
         const socket = this.socket = io.connect(this.baseUrl, { forceBase64: true });
 
         socket.on('connect', err => {