design: Remove window titles

[WatchMkr]

Remove window titles from the app and file selection dialogs.

All context should be provided in the app or from the action taken just before (clicking "Open" for instance makes it obvious that the following file dialog is for opening a file). If not, the app design needs to be improved.

[maria-komarova]

Looks to me that this has been done. The only places where it remains and may be useful is Context drawers but we can create separate issues for those.