[ticket/12507] Add console command to purge the cache

PHPBB3-12507
[ticket/12507] Move the 'require' statement

PHPBB3-12507
Merge pull request #2416 from Nicofuma/ticket/12507

[ticket/12507] Add console command to purge the cache

* Nicofuma/ticket/12507:
  [ticket/12507] Move the 'require' statement
  [ticket/12507] Add console command to purge the cache