fixed last column width display bug

Change-Id: Ib3af8e9f4da4e5a35105b185f52c36f9948df66d
partition data source editor now implements
IObjectWithSelectableAtttributes

Change-Id: I66ea947fcf2707922048ff528e98f77d7c9411ec
fixed bug where columns wouldn't be updated when data source was
modified.

Change-Id: I1b585dd126b6ca15e42606a97188320b9d845c59