Offline use

[hugovk]

I'm submitting a ... (check one with "x")
[ ] bug report
[x] feature request
[ ] support request => Please do not submit support requests here, use one of these channels: https://forum.ionicframework.com/ or http://ionicworldwide.herokuapp.com/

It's possible to imagine there may be patchy internet with lots of people using the same wifi/cell data at a conference.

Also, there will be many people travelling internationally who may be limited in using roaming data.

Current behavior:

With data turned off, shows:

"Schedule not loaded, if this persists check your network."

Expected behavior:

It would be nice to cache the conference schedule data from the last time we had a connection, and load it in the case of no network, so we can still check the schedule.

Steps to reproduce:

Turn off data and open the app.

[miketheman]

Blocked by #43

Current schedule cache mechanism uses non-reliable storage.