[ticket/12374] Add Template events index_body_block_(name)_append

Hopefully to the correct branch this time

PHPBB3-12374
[ticket/12374] Updated code layout

PHPBB3-12374
[ticket/12374] Added prepend-versions of events

PHPBB3-12374
[ticket/12374] Fixed alphabetical sorting

PHPBB3-12374
Merge pull request #2270 from PayBas/ticket/12374

[ticket/12374] Add Template events index_body_block_(name)_append

* PayBas/ticket/12374:
  [ticket/12374] Fixed alphabetical sorting
  [ticket/12374] Added prepend-versions of events
  [ticket/12374] Updated code layout
  [ticket/12374] Add Template events index_body_block_(name)_append