Improve the activity log

[gacelita]

Right now it's useless, as it only lists entity transaction events. The activity log should register more events and describe properly the ones it already registers.

For entity creation, a link to edit the entity could be provided, along with what data it included when it was created.

Same for updates: show what was updated. Show the time when this happened.

Both creation and update events should be far more semantic. If an user is created, is it because a user was registered? Or something else?