When different ID's are set for each sequence a number
of unit test failures appear. They have been corrected
to allow unit tests to pass with the new generator in place.
When there are many files inside a single resource, it's possible
for the backup to time out because it does not report progress
while adding entries to the backup_ids table.
Adds calls to the new backup progress tracking API within various steps of the
backup system - previously it only tracked progress between steps, but some steps
can themselves be slow. This ensures the system displays progress (either by
moving the progress bar if possible, or by making the wibbler below it pulsate)
during nearly all of the backup process.
An activity module might want to use question_usages in different ways.
We should suppport this, because it lets people make interesting
activities.
At the moment, the backup and restore code does not support this,
because it uses fixed element names for the question_usage element and
its children. This fix changes things so that a prefix can be appended
to all the element names.
