Fixed Bugs

#2624 Iteration Burn Down chart shows incorrect remaining hours when user story with tasks has own effort
#2626 Subversion: "Could not change state from Source Control" comment added sometimes
#2629 UI error when deleting a task in user story view
#2630 Refresh doesn't happen when deleting items in user story view
#2631 Impediments popup shows the impediments for user story instead of task's impediments in user story view