Also deprecated the following functions -
1. message_move_userfrom_unread2read - It is not necessary
for us to mark a message as read on user deletion.
2. message_get_blocked_users - Horrible logic used to
determine if a user is blocked via reference on some
randomly chosen 'isblocked' variable.
3. message_get_contacts - The same as above. This can be
done in a much nicer way.
4. message_mark_message_read - We want two functions to do
this to avoid confusing messages and notifications.
5. message_can_delete_message - This assumed the variable
$message contained the 'useridto' property, which
was present in the old table structure. We do not want
future usages where a query is done on the new table
and is simply passed as this won't contain this property.
6. message_delete_message - Same as above.
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.
