[Distutils] Additional trove classifiers for Plone

["Martin v. Löwis"]

> To be a bit more specific: the proposal is to use the same scheme as
> used to indicate Python version compatibility by extending the Plone
> framework classifier with version numbers. For example:
> 
>   Framework :: Plone :: 4.1
>   Framework :: Plone :: 4.2

Can you please be even more specific? Someone please provide an exact,
complete list. I have no clue what version numbers Plone uses.

Regards,
Martin