* src/sheet-object-graphic.c (sheet_object_filled_user_config,
sheet_object_graphic_user_config): Make <return> in text entry, spin
button fields activate default.

* src/sheet-object-widget.c (sheet_widget_adjustment_user_config,
sheet_widget_checkbox_user_config): Make <return> in text entry,
expression entry fields activate default.

* src/dialogs/autofilter-expression.glade: Set has_default for ok_button.

* src/dialogs/autofilter-top10.glade: Ditto.

* src/dialogs/pivottable.glade: Ditto.

* src/dialogs/so-frame.glade: Ditto.

* src/dialogs/solver.glade: Ditto.