R1:7fcc0f9ebd91

Remove "PhabricatorFile->detachFromObject()"

Summary:
Ref T13603. Currently, files are sometimes detached from objects. For example, when you change the image for a Macro, the old image is detached.

This is wrong: the image should remain attached so users who can view the macro can view the complete "alice change the image from X to Y" transaction. To be able to understand the change that was applied, you need to be able to view both files.

All workflows which currently detach files aren't conistent…