Logviewer should suggest crontask rather than requiring it

[robbieaverill]

The purpose of the crontask is that if you've got the module installed, you can run the clean up build task as a cron task as well. It shouldn't require it as a dependency though.

[zanderwar]

Any reason why we can't move this to require-dev ?

[robbieaverill]

Yeah the BuildTask implements CronTask at the moment, initially it was to save duplicating the code. We'd need to separate that and create a separate CronTask implementation which we could then suggest crontask instead using