UX fix: Finally adds some sane handling of Dialogs all over the GUI

For some reason when we added any Dialog (pop up that opens in the GUI. See attached.), we do not allow the default behavior according to standard UX practices all over. Now, as a user will expect, you can hit the "Esc" key or click outside a Dialog to have it dismissed.

For some cases, this is not ideal. I found such cases and ignored them. One was the upload progress dialog. There were also a few places where explicit code handled the dismissal behavior, like the App Dashboard from @himanel1. I didn't change those.

@himanel1 @mscheidg @mnakh please have a look if I have got this correct and not overridden a prevention of dismissal of these dialogs you might have intended.