This mostly works now, but ...
* The UI needs further work. In particular we need a non-advanced mode.
* This only works for blocks that use a new edit_form.php to replace config_instance.html.
* .. and so far I have only implemented edit_form.php for the HTML block so far.
* Needs to be enabled (with no block-specific config) for blocks without instance config, so you can control their positioning.
Martin Dougiamas