Persisting state for ionic PWA

[robinyo]

@Slavrixx

See:

• https://medium.com/@cyrilletuzi/angular-2-async-local-storage-fd8609fa84e0
• https://github.com/cyrilletuzi/angular-async-local-storage
• https://developers.google.com/web/fundamentals/instant-and-offline/web-storage/offline-for-pwa

And:

• https://stackoverflow.com/questions/6930771/stop-reloading-of-web-app-launched-from-iphone-home-screen
• Caching nav state for ios PWA