Reports sync failed notification.

Displays bar with error message and a retry button when sync fails. Closes #376 
Instead of `frag.LoadReady += lambda;`, this should be `frag.LoadReady += SomeFunction;` and you should also unregister the `frag.LoadReady -= SomeFunction;` somewhere.

The lambda here has potential memory leak written all over it with the fact that the more you reload the data in attempt to get it the more listeners you register.

I'm thinking the best for those are the `InstantiateItem` and `DestroyItem ` in `MainPagerAdapter`. The `MainPagerAdapter` then should re-expose the LoadReady as it's own delegate/event where it also passes fragment position (?) from which the event originated.