Implement Watchlist and stored searches

1. A user can define several watchlists.

   • Each watchlist has a name.
   • A user should be able to put exercises onto a watchlist. Also he can remove exercises from the watchlist.
   • A watchlist can be deleted
   • A user can set an alarm, if an exercise on his watchlist was updated. The alarm is executed nightly.

2. A user can save a search.

   • The saved search can be used, to requery this search later. A saved search can be deleted.
   • The user can set an alarm on the saved search. It is triggered, if the saved search find's a result that is (configurable)
     • either updated
     • is completely new