Updated ftw.zipexport registry entry to multi-value field.
Merge pull request #258 from 4teamwork/lk_update_zipexport_registry

Updated ftw.zipexport registry entry to multi-value field.
Don't pin setuptools&co any more.
Fixed LDAP credentials example in README.
Fixed interface in dossiers ConstrainTypeDecider.

The default adapter should use `Interface` as adapting interface
for the request. Otherwise overriding the ConstrainTypeDecider
in a customer package, is not possible without inheriting from
`Products.CMFDefault.interfaces.ICMFDefaultSkin` in the customers browserlayer.