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- Added `BaseARUOBatchActionForm`, a class factorizing the action that
`add/remove/update/overwrite` values on an attribute of an object
(originally used for the `LabelsBatchActionForm`) so it is easier to reuse
for other similar actions. `LabelsBatchActionForm` is now based on that
`BaseARUOBatchActionForm`.
[gbastien]
- Activated `delete-batch-action` for zope admin
[sgeulette]