- Added page 4 of the wizard (grid) and adjusted relevant parts of the code to accomodate this page
- Added support for selection by country:
 - Added list view, supporting multiple selection; this list view is fed by "g0000_0.shp"
 - created memory layer, whose geometry copies the result of filtering "g0000_0" with the selected countries.
 - applied clipping operations to the project layers, with the created "selection_layer"