[ticket/13116] Interchange post and topic approval notification

PHPBB3-13116
[ticket/13123] Add events to allow modifying post data

PHPBB3-13123
[ticket/13119] Add another event which is triggered independent from actions

PHPBB3-13119
Merge pull request #3015 from nickvergessen/ticket/13119

[ticket/13119] Add another event which is triggered independent from actions
Merge pull request #3012 from nickvergessen/ticket/13123

[ticket/13123] Add events to allow modifying post data

* nickvergessen/ticket/13123:
  [ticket/13123] Add events to allow modifying post data
Merge pull request #3004 from Senky/ticket/13116

[ticket/13116] Topic and post approval notifications got interchanged