#4837, #4838, #4839, #4840: saving usability improved

- Fixed table view double-click (+better performance there)
- Fixed loading non-graph objects to scene at (0,0)
- Updated version to 0.1.5
- Added File/New menu entry
- Added File/Save as... menu entry
- User is friendly asked to save changes whenever he can lose data
- When saving file statusBar shows message about completed operation
- Mainwindow's title is changed according to currently opened file. File
is marked by '*' if it was changed.