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- Added `BaseColumn.escape = True` so content is escaped.
Manage escape manually for the `TitleColumn`, `VocabularyColumn` and the
`AbbrColumn`, set it to `False` for `CheckBoxColumn`, `ElementNumberColumn`
and `ActionsColumn` that are entirely generated, set it to `False` for
`PrettyLinkColumnNothing` as `imio.prettylink` manages it itself.
[gbastien]