Automated e-mail notifications

[MaxVMH]

The thought is to make a seperate user_league_notification table to link user_id with league_id and notification_datetime_offset & notification_sent so that users can choose when they want their notification of a certain league.

[MaxVMH]

Also needed: a clear explanation on how to set up e-mail notifications should be provided upon registration, on the edit e-mail page and in the FAQ.

[MaxVMH]

To make it automated I need to make a cron.php file that contains an execution of the e-mail notifications

[MaxVMH]

Cron job allows for automation in commit e458661. This removes the priority label.

This issue can stay open with enhancement label until e-mail notifications get a rework (so people can choose when they receive notifications for which leagues).