IOS: nativeScriptBootstrap promise is not resolved

[vakrilov]

nativeScriptBootstrap promise is not resolved in IOS.

nativeScriptBootstrap(RendererTest).then((comp) => {
    console.log("XXXXXXXXXXXXXXXXXXXXX START XXXXXXXXXXXXXXXXXX");
})

It works on Android though

[vakrilov]

Reported originally in #156

[vakrilov]

Copying the comment form the PR here for clarity:

There is a limitation in IOS: Any code executed after application.run() will not be executed in IOS. As application.run() is called inside nativescriptBootstrap there is no point to return promise from this method - the promise can never be consumed.

The code that is to be executed on app startup can be moved inside the app main component.