'Needed for' field, generated from 'depends' field

* Displays in plugin entry the plugins that depends on that plugin
    *  implements #14
    * shows metainfo aggregated from the existing depends field
    * inclusive dutch translation.

Use case: 
For example the plugins data, dataloop, datatemplate, do (and more) depends on the sqlite plugin. But there isn't a searchquery on dokuwiki.org that will catch all the usages of the sqlite plugin. This `Needed for` field will query pluginrepos database and return the desired info.