Due to imperfect validation of the user registration and profile forms,
we allowed for firstname and lastname be just a whitespace. On MySQL,
such a whitespace is not significant for VARCHAR comparison so these
otherwise valid accounts could be silently deleted.
The patch makes sure that at least one of the checked fields is a real
empty string before deleting such account.
Centralise management of all types of cron tasks with registration, scheduling,
parallel task conflicts(blocking) and running once off tasks, all using an
administration screen.
This is a combination of several issues:
MDL-25502: Added "black magic" task allocator for cron
MDL-25503: Add step to cron to run all scheduled tasks
MDL-25504 cron: Refactor to use scheduler
MDL-25505: Add an admin interface to schedule tasks via cron.
MDL-25507: Add support for adhoc tasks.
