Support LMS auto logout

This task should be tested in Android & iOS.

Test with a 4.3 site
We have 3 use cases depending in which auto logout type is selected by the admin in Site administration > Mobile app > Mobile authentication > tool_mobile | autologout:

1. Custom time after users leave or close the app: 
   • Admin set 2 minutes of session duration. User enter to the app, and close it. (the following use cases include background mode and kill the app)
     • If the user leave the app for 1 minute and then open again the app, he won't be requested to login again.
     • If the user leave the app for more than 2 minutes and then open again the app, he will be requested to login again.
2. Immediately after users leave or close the app:
   • User enter to the app, and close it.
     • If the user kill the app, then he will be requested to login again.
     • If the user sent the app to background, he will have a "grace period" of 30 seconds to comeback to the app, if the "grace period" expire, then, he will be requested to login again, if not expire, he won't be requested to login again.
3. Never:

• • The app should work like before.

Test with LMS <4.3
It should work like 'Never'.