Issue #73 Add new notification migrations
Issue #73 Update notification models

Add user_notification model, change notification model (add acts as superclass, users assosiation), remove users assosiation from user and idea notifications and add inheritance from notification
Issue #73 fix inheritance in idea/user notifications subclasses and remove IdeaNotification inheritance from DeleteNotification
Issue #73 Update assoiations, add dependent destroy
Issue #73 Remove delete notification view from idea_notifications partial and create a new one for delete notifications
Issue #73 Update notification methods to use user.notifications
Issue #73 Add MTI gem
Issue #73 change read_for to set_read_for
Issue #73 add redirect_expertise to render expertise modal dialog