Controller: save all modified indicator fix

Unset modified attribute from all editor tabs when save all is called
When we call SaveAll in IDE, in the end it was reaching to [this](https://github.com/koding/koding/blob/newkoding/client/Ace/AppView.coffee#L96) line, and it only removes modified indicator from activeTab. 

We have spoken with Acet and decided to handle it in IDE, but I do not know much about methods of ace, like this saveAllFiles method.