This patch replays the logic of resource_20_migrate() function. If a
file is referred via URL to the course files of the course being
backed up, then such a resource is converted to the File module
(mod/resource) rather than URL module.
During the restore, the section's sequence field is ignored and the
order of modules is controlled by the order of the <contents> activity
elements. This patch makes sure that the modules are listed in that
section in the right order.
Also, the patch removes the obsolete stash sectionidslist which was
introduced when the method get_stash_itemids() had not existed yet.
David Mudrak