Implement subscription of station.

[ljellevo]

When a user subscribes to a station should the timestamp for start of subscription + notification duration be posted. This way the push system knows when to stop sending notifications.

[ljellevo]

Missing: Sending notification when subscription has run out

[ljellevo]

Also need to implement countdown and filtration of subscriptions. Only active subscriptions should be shown.

Favorite and subscribe button should also have an indicator in case internet is slow and user is waiting for confirmation

[ljellevo]

Need to sort subscriptions after "from" parameter

[ljellevo]

If sub runs out and user is in favorites view then confirmation box is shown. This needs to be solved.

[ljellevo]

Need to move automatic unsubscribing to backend