The events should cover all of the following cases:
- block is added to the course page, frontpage, or any other page
- block configuration is changed (this also includes visibility)
- block position is changed *)
- block is removed
- blocks are added/configured/removed on "My home"
- blocks are added/configured/removed on "Default My home page" (/my/indexsys.php)
- block configuration is changed
*) this is a tricky event similar to the events "module moved" and "section moved". Moving one block involves changing weights on several blocks. We might decide only to trigger event if the "region" is changed and ignore the changes in "weight"