Some fixes in the add prop. to sdf wizard

This pull request contain this changes:
* The exclude-button becomes an include-button.
* The columns in the properties preview scales with the window.
* The dummy text in the properties preview (i.e. the text when no prop.-file is loaded) is removed.
* No error-message visibly when opening the wizard.

I.e. it fixes bug 3481 and some more things.