JIRA backup and restore does not handle map data stored by plugins correctly

If a plugin developer uses SAL to store a map in the database using PluginSettings.put(key, value) where value is a Map then the values in the map are stored in the database using a separator of x'0C', aka \f or FormFeed. This character is invalid in XML including within CDATA and EntityEngine does not handle this data in any special way on Export and so on XML restore the data becomes invalid and inaccessible to the plugin.