fix few bugs and added new Featuers:
1.adding icon
2.showing and saving updates 
3.when getting update for prev-post ,downloading the new info about it
4.adding new class notification for courses 
5.showing notification for update from background and from foreground
6.alarming about workshop before 20 minutes in specifec date 
7.saving the notified courses(groups)

TO-DO:
1.moving the updates data structure to sorted list descended by date
2.when un-subscribe to course set the notify 0 in db (new list of trash)
3.testig alarms for workshops
4.pictures for courses 
5.cleaning the code 
and many ...