Use permanent storage on phone with javascript to backup card entries

[LiyouZhou]

new sdk allows permanent storage on the phone using javascript

http://www.w3schools.com/html/html5_webstorage.asp

[jgillard]

Initial thoughts:

• Download and upload data between watch and phone on config page open & close, as we do now.
• Save card data to localStorage on config page submit (also store watch ID).
  • Allows new or reset watch to be synced again.
  • New watch: prompt to reload cards from localStorage
  • Same watch: if empty card list.... depends on on-watch deletion: #7

This makes minimal use of localStorage.

The opposite of this is do most of the work in localStorage, and then only sync back to watch on config page submit. i.e. not download from watch at all. Needs #7 and #8 closed for consideration of this method.

https://developer.getpebble.com/guides/pebble-apps/pebblekit-js/js-capabilities#storing-data

[LiyouZhou]

when watch resets is a good usecase. This happened to me a few times, when I reinstalled the app, all cards are lost.