feat(additional-attributes): add test for "additional static attributes and remove old disabled tests

[HellButcher]

• removed disabled tests.
  replaced by new tests, that use the explicit pl:pass-additional-attributes attribute
• pick correct fragment in file, and validate signature (required parameters inside ())
  (similar like th:insert and th:replace works)
• set TemplateData to allow to correctly resolve relative templates (~{::fragment-name})
• use seperate tag-processor for replacing slots.
  more roboust: only slots that survive evaluation (th:if) are replaced;

[cstettler]

Hi @HellButcher, thank you very much for your valuable contributions! I will try to review and merge them as soon as possible. For the future, it would be easier to get smaller and more atomic pull requests (quickly describing the relevant what and how, as you already did). That would also allow faster review and faster merge. Thank you!