Expand module names instead of buttons in settings

Maximizing the document settings window when on the modules pane,
the horizontal space is now given to the module names and so no
scrollbar is needed. Before, even when maximized, a scrollbar was
sometimes needed because the horizontal space was given to the
buttons in the middle, which did not provide an extra benefit.

The default sizeType was "Expanding" and is now changed to "Minimum"
for the horizontal spacer above the middle buttons.

src/frontends/qt4/ui/ModulesUi.ui

@@ -92,6 +92,9 @@
            <height>20</height>
           </size>
          </property>
+         <property name="sizeType">
+          <enum>QSizePolicy::Minimum</enum>
+         </property>
         </spacer>
        </item>
        <item>