[ticket/12597] Do not output anything besides the gif image.

PHPBB3-12597
[ticket/12597] Improve language for cron:run command.

PHPBB3-12597
[ticket/12597] Update USE_SYSTEM_CRON_EXPLAIN to be a bit more verbose.

PHPBB3-12597
Merge pull request #2523 from bantu/ticket/12597

[ticket/12597] Command for executing all available cron tasks

* bantu/ticket/12597:
  [ticket/12597] Update USE_SYSTEM_CRON_EXPLAIN to be a bit more verbose.
  [ticket/12597] Improve language for cron:run command.
  [ticket/12597] Do not output anything besides the gif image.