Add checkboxes or radio buttons on "MenuPage" of gtk_ui.py to operate intutively.

Fixed Bug #813771 according to suggestions shown in its bug report thread. I added these modifications,

1. Changed the way of selection from TreeView's to checkboxes.
2. Highlight the selected rows.
3. Add toggle changes when clicking on anywhere of the row.
4. Add the selection pattern on the MenuPages, which can choose both nothing and a single row only.