Add onBeforeDelete and onAfterDelete for plug ins

[schnuti]

MM adds onBeforeSave and onAfterSave events but onBeforeDelete and onAfterDelete are also needed.

One example that might be of interest those days. (EU's GDPR)
A plug-in keeps track of the created (uploaded) files in a db table including user-id (right to information on own data).
A second plug-in should check user authorization before deleting the file and delete the table entry after deleting. (right to remove data)

How to delete all user data including his uploaded images is a much larger issue.

I find this relevant but there are other examples where the delete events would be needed. #

[schnuti]

Do not forget the not yet implemented Cut/Copy/Paste functionality. The events are needed there as well.