Kudos to Mark Nielsen for his initial work on this project. In his code,
Mark described the valuable logic of the conversion using a framework
mirroring plan/tasks/steps based architecture of the backup and restore.
My attempt to simplify it led to the current handlers-based
architecture.
Added write_xml() helper that writes the given tree-ish structure into
the current xml writer. Improved get_contextid() so that it can use
indices for searching data. Added set_stash() and get_stash() helper
methods.
This patch mainly adds support for dispatching path-start and path-end events,
defines API to access backup_ids_temp table. Some ideas emailed by Mark
after his first review of the code are incorporated already.
These are David's changes of Mark's code that replace the
plan/tasks/steps infrastructure with a bit simpler one. The changes will
be described in the next commit that will actually finish the
conversion.
TODO: refactor backup/converter/moodle1/stepslib.php into conversion
handlers.
* Several base_converter methods made protected when there was no obvious
reason why they should be public (subject of eventual change still).
* The conversion chain now constructed in advance before any converter
class is instantiated, using Dijkstra's algorithm.
