Update import for INameChooser for Plone 4.3

Plone 4.3 removes many outdated packages and tidies up imports: http://plone.org/documentation/manual/upgrade-guide/version/upgrading-plone-4.2-to-4.3/updating-package-dependencies
This change will need to be revised if Plone 4.0 support is required for plone.api