The signature of mod_workshop_mod_form::validation() is now compatible
with that of moodleform_mod::validation() even though the parent's
declaration sucks. No one can choose their parents.

Based on http://commons.wikimedia.org/wiki/File:Appointment-new.svg
(public domain Tango! Desktop Project icon)

Note that most line changes in the patch are caused by the recent
changes in the XMLDB TEXT fields handling (no size specified now) and by
the change in the indentation.

AMOS BEGIN
 CPY [allocationsettings,workshopallocation_random],[randomallocationsettings,workshopallocation_scheduled]
AMOS END

Removing the table "scheduled" created by the XMLDB by default (it's a
bug in XMLDB, I'm just too lazy now to fix it). Adding new fields to
hold the result of the most recent execution.

On every invocation, the workshop will give its subplugins a chance to
to something useful. For now, we know that the scheduled allocator will
use it, no need to load other plugin types yet (until there will be a
real reason for it).

The idea is to build a plugin that will internally call the random
allocator when the submissions deadline is reached. The teacher is able
to pre-define the configuration for the random allocator.

The new renderable class workshop_allocation_result provides a cleaner
interface between the allocator's init() method and the allocation.php
script.

The random allocator's init() method was split into two logical
parts. The init() now handles data from the form and executes the new
execute() method to do the actual job. The execute() method will be
called by the future scheduled allocator, too.