add feature_id attribute to swisssearch index
change datasource zipcode
remove empty attribute
Revert "remove empty attribute"

This reverts commit 99a6abe628bcfd517a78cf4b77758edfba791ae0.
Merge pull request #118 from geoadmin/dev_ltclm_swisssearch_add_feature_id

add feature_id attribute to swisssearch index