Reintroduce an aq_inner into the getPhysicalPath code to fix test failures in CMF's discussion items

Optimized the `OFS.Traversable.getPhysicalPath` method to avoid excessive amounts of method calls. Thx to Nikolay Kim from Enfold

Removed the `App.version_txt.getZopeVersion` API, you can use ``pkg_resources.get_distribution('Zope2').version`` instead. Zope2's own code only calls the `version_txt` function returning a string.

On the application object, removed `PrincipiaTime` in favor of `ZopeTime` and `PrincipiaRedirect` in favor of `Redirect` or `ZopeRedirect`.

Removed `mime-types` option from `zope.conf`. You can use the `add_files` API from `zope.contenttype` instead.