Introduces 'multi_edited.{event} > {$edit_method}' event.

Now on just the Articles panel. Can be used to detect
any multi-edit action instead of just deletes. The handlers
get passed on three normalized values: $selected, $field
and $value.

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5316 2fea6a4d-a838-0410-917b-93a53c48e9d2