updated timeline-view to operate on "created_at" + 2 fixes

Fixes:
- corrected label of button pointing to new detail-view
- properly declared local var's in all for-statements
- user input of two _new_ literally identically tags is now prevented

Pending:
- extend app about "last_modified" info on each resource
- allowing adding license and web-page infos to resources via gui
- allow users to manipulate the tag-filter per item
- enable users to edit and delete tags in single-resource/detail view

Testing continues.