Collective-iconifiedcategory

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- Use a specific static resourceDirectory for images.
[gbastien]

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- Call `actionview._may_set_values` in `IconClickableColumn.is_editable`
to avoid double logic.
[gbastien]

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- Fixed migration that adds `to_sign/signed` relevant data to the
`categorized_elements` of the parent containing categorized contents.
Execute the update with `limited=False` and do not care about already
migrated content, do the update on every found elements.
[gbastien]
- Added tests for the `SignedChangeView` view especially the `loop` among
possible `to_sign/signed` combination values.
[gbastien]
- Do not break when deleting an element having a `content_category` if container
does not have the `categorized_elements` dict.
[gbastien]
- Improved some translations.
[gbastien]
- Factorized the way categories and subcategories are get for the
`content_category` vocabularies `collective.iconifiedcategory.categories` and
`collective.iconifiedcategory.category_titles` so it is easy to override and
we rely on same method for both vocabularies that needs same source.
[gbastien]

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- Added management of `to_sign` and `signed` attributes like it is the case for
`to_print` and `confidential` attributes. Both attributes are used behind a
single action `signed` that have 3 options : `not to sign`, `to sign` and
`signed`.
[gbastien]
- Default values for `to_print`, `confidential` and `to_sign/signed` are now
managed in the `IObjectAddedEvent` no more in the `content_category setter`,
this way every attribtues are managed the same way because `to_print` and
`confidential` are simple attributes where `to_sign/signed` can come from the
`Scan metadata` behavior of `collective.dms.scanbehavior`.
[gbastien]
- Added possibility to show/hide details about `to_print`, `confidential`,
`to_sign/signed` in the categorized elements tooltipster.

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- Make portal available on the tabview instance.
[gbastien]

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- Reverted changes from releases `0.19` and `0.20`, we do not bypass can_view if
element is not `confiential` because `can_view` could take into account other
elements than `confidential`.
[gbastien]