change moderator to editor, and curator to moderator

app/policies/activity_policy.rb

app/policies/application_policy.rb

app/policies/bookmark_policy.rb

app/policies/collection_policy.rb

app/policies/institution_policy.rb

app/policies/language_policy.rb

app/policies/learning_object_policy.rb

app/policies/license_policy.rb

app/policies/mime_type_policy.rb

app/policies/object_type_policy.rb

app/policies/publisher_policy.rb

app/policies/rating_policy.rb

app/policies/search_policy.rb

app/policies/submission_policy.rb

app/policies/user_policy.rb

app/policies/welcome_policy.rb

app/serializers/collection_item_serializer.rb