[ticket/11716] Convert Soft Delete Mod to post/topic visibility

PHPBB3-11716
[ticket/11716] Rename migration files and add note that it's converting a MOD

PHPBB3-11716
[ticket/11716] Fix dependencies in migration files

PHPBB3-11716
[ticket/11716] Correct license URL

PHPBB3-11716
Merge remote-tracking branch 'EXreaction/ticket/11716' into develop

* EXreaction/ticket/11716:
  [ticket/11716] Correct license URL
  [ticket/11716] Fix dependencies in migration files
  [ticket/11716] Rename migration files and add note that it's converting a MOD
  [ticket/11716] Convert Soft Delete Mod to post/topic visibility