[ticket/12150] Add options to acp

PHPBB3-12150
[ticket/12150] Add prune columns to schema files and migration file

PHPBB3-12150
[ticket/12150] Add file and caller for pruning shadow topics

PHPBB3-12150
[ticket/12150] Add missing prune settings variables in acp_forums

PHPBB3-12150
[ticket/12150] Add missing space to query for shadow topics

PHPBB3-12150
[ticket/12150] Add functional tests for pruning shadow topics

PHPBB3-12150
[ticket/12150] Use shorter column names for prune settings

All columns were renamed from having prune_shadow_topics as namebase to just
prune_shadow.
A missing column was also added to the migration file's remove_schema() method.

PHPBB3-12150
[ticket/12150] Use log service instead of add_log() function

PHPBB3-12150
Merge branch 'develop-ascraeus' of https://github.com/phpbb/phpbb into ticket/12150
[ticket/12150] Update schema files for prune shadow topics

PHPBB3-12150
[ticket/8700] Remove unused language strings

Most of the strings were obsoleted by the removal of:
* Imagesets
* Themes
* Templates
* Editor
* Exporter

PHPBB3-8700
[ticket/8700] Use L_COLON instead of adding ":" manually

PHPBB3-8700
[ticket/12150] Remove 'after' for columns from migrations file

PHPBB3-12150
[ticket/12349] Update license header in several new files

PHPBB3-12349
[ticket/12349] Fix Sniffer for @license tag

PHPBB3-12349
[ticket/12150] Use correct license URL in prune shadow migrations file

PHPBB3-12150
[ticket/12354] Assert same instead of equal where necessary in passwords tests

In some tests we try to make sure that we do not get the same output in a
limited timeframe. These tests should use assertSame/NotSame instead of
assertEqual/NotEqual.

PHPBB3-12354
[ticket/12083] Fix Select All in CODE bbcode with only one char

PHPBB3-12083
[ticket/12362] Throw exception in schema generator on unresolvable dependency

Make sure we throw an exception in the schema generator if we come across an
unresolvable dependency. Otherwise we'll get stuck in a infinite loop that
needs to be cancelled by the user or the maximum execution time.

PHPBB3-12362
[ticket/12364] Add template identifier var to all missing pages

PHPBB3-12364