Improve startup in JavaScript

[brodycj]

The requirement to wait for the deviceready event has caused some major confusion and other trouble for people using Ionic 2 and other Angular derivatives with the sqlite plugin. Here are a couple examples:

• openDB don't work in android storesafe/cordova-sqlite-storage#598
• Getting message: Native: tried accessing the SQLite plugin but it's not installed. ionic ios emulator 10 storesafe/cordova-sqlite-storage#594

I think storesafe/cordova-sqlite-storage#594 (comment) by @rodineijf really helps to highlight this problem:

Hi @brodybits, by default the attribution of rootPage on ionic 2 is on declaration of var rootPage. I can solve my problem moving the rootPage attribution to the platformReady on app.component

initializeApp() {
this.platform.ready().then(() => {

  this.rootPage = MyPage;
  StatusBar.styleDefault();
  Splashscreen.hide();
});
}

In contrast I heard that in the React Native there is no requirement to wait for the deviceready event.

I think the solution is to fix cordova.js to prepare the all of the JavaScript from the plugins upon loading and to have cordova.exec put the native calls into a queue until the initialization is confirmed to be completed.

I will take a look at fixing this when I get a chance.