Fixed Bugs

#1972 Dashboard exception: The parameter with Project name is added already
#1960 Edit User: "working hours" field is not saved
#2026 NullReferenceException in impediment icon in Iteration view / user stories tab
#2027 ArgumentNullException when change Iteration in Daily Progress report
#2036 Edit user story problem: A different object with the same identifier value was already associated with the session of class: Tp.BusinessObjects.Comment