[allowed] Allow Nemo D-Bus QML Plugin (API version 2.0)

With version 2.0 of the QML import, we have reviewed and stabilized the API:
https://github.com/nemomobile/nemo-qml-plugin-dbus/pull/21

Do not merge yet, will have to wait for the pull request above to be merged and tagged. Also, this is only available from a given (future) SFOS release version, as old versions do not have the 2.0 API import.