Option Page Group Plugin Extension
This type of plugin extension allows you to add a group of custom Preferences pages from a plugin.
The extension must implement the
        ro.sync.exml.plugin.OptionsPageGroupPluginExtension class. The base method
        OptionsPageGroupPluginExtension.addOptionPagePluginExtension(...) allows
      adding multiple implementations of the OptionPagePluginExtension base class.
All preferences pages that are contributed by this extension are listed as descendents of the plugin specific preferences page in the Preferences dialog box in the Plugins category.
The plugin.xml configuration file can specify one or
      more such extensions using constructs like
      this:
  <extension type="OptionPageGroup" class="my.pack.CustomOptionPageGroupPluginExtension"/>