Individual items in the bar can now be configured with a prefix and a
suffix. It works like this:
* If there is a specific module configuration in the theme
configuration, use that (i.e. { "<modulename>": { "prefix: " a " } })
* Otherwise, if there is a configuration in the "default" section of the
theme, use that
* Otherwise, if the module object itself has a method called like the
required attribute (prefix, suffix), use that
* Otherwise, leave prefix/suffix empty ("")
