Imio.helpers

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- In `xhtml.storeImagesLocally`, take into account `<img> src`
that uses `resolveuid`. This is the case when using `collective.ckeditor` and
option `allow_link_byuid` is enabled.
[gbastien]
- Do not use `/* ... */` together with `https://` in helpers.js comment or
merged javascripts produce a wrong format and raise a JS comment unterminated
error in the browser.
[gbastien]

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- Added method `testing_logger` to `testing.py` that enables logging into tests.
[gbastien]

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- Changed method `xhtml.storeExternalImagesLocally` to
`xhtml.storeImagesLocally`, it handles now external and internal images
retrieval so an image stored in the portal is also created in given context
when necessary.
[gbastien]

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- Added method to safe encode string.
[sgeulette]
- appy.pod usecase : table using width of 0px.
[gbastien]
- In `content.validate_fields`, added special bypass to avoid failing
validation for `Choice` field that is `required=False` and for which given
value is None. Validation fails because None not in vocabulary but it is
nevertheless a correct value as it is managed by the widget while added thru
the UI.
[gbastien]
- Added JS fix to be able to print `<fieldset>` on several pages in Firefox,
see https://bugzilla.mozilla.org/show_bug.cgi?id=471015.
This makes it necessary to add a default profile to add the JS resource
`++resource++imio.helpers/helpers.js`.
[gbastien]

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- Get intid value or create it if not found.
[sgeulette]
- Added possibility to pass 'scale' value to pdf.BarcodeStamp.
[gbastien]
- More appy.pod usecase : not rendered sub bullets with no parent bullet.
[gbastien]

-------------------

- Added method to create NamedBlobFile or NamedBlobImage.
[sgeulette]