More modernization

- Split generic "common" libraries into specific libraries
- Use other packages in lieu of custom code
- General cleanup

Application/Options/GeneralOptionsPanel.xaml

@@ -38,8 +38,6 @@
                   Grid.Row="2"
                   Grid.Column="1"
                   VerticalContentAlignment="Center">
-            <ComboBoxItem Content="{x:Static properties:Resources.DefaultBrowserCaption}"
-                          Tag="" />
         </ComboBox>
         <Label Content="{x:Static properties:Resources.defaultUserAgentLabel}"
                Target="{Binding ElementName=BrowserComboBox}"