Project View Usability: improve view managment

The view management system with the project tree is not intuitive enough. It was tested on biologists who see UGENE for the first time.

So the following improvements are suggested:
1. Double click on any place (sequence, annotation, document itself) of document cause opening of the view
2. This double click does not call a context menu to select an opened view or create a new one. It opens the first view if it exists or create a new one otherwise.
3. The context menu of a document is also incomprehensible. I must be grouped somehow and reordered.