Plone.namedfile

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* Use plone.app.imaging's (>=1.0.8) quality setting if it exists.
https://dev.plone.org/ticket/13337
[khink]

* fix invalidation on contexts that do not implement dublin core; Notably
portlet assignments. Fallback is bobo_modification_time. Maybe portlet
assignments should implement modified() instead?
[tmog]

* Fixed handling of TTW Dexterity content type image field
data when image data is large and stored as
zope.app.file.file.FileChunk in ZODB instead of raw string data.
Issue appearated after Plone 4.3 migration [miohtama]

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* Add direction parameter support in scaling (was ignored in tag and scale
functions).
Now calling tag function with parameter direction='down' crops the image.
direction='thumbnail' by default so default behaviour remains the same.
[jriboux]

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* Move file and image value implementations here instead of extending
the ones from zope.app.file and z3c.blobfile. This helps tame a mess
of dependencies.
[davisagli]

* The blob-based file and image implementations are now always available.
(But they will only work if Zope is using a storage with blob support.)
[davisagli]

* Add support for HEAD requests to images view
[anthonygerrard]

* Add hook to override headers in subclasses of file download view
[anthonygerrard]

* Don't set filename in header if filename contains non ascii chars.
[do3cc]

* Adding Dexterity Image caused TypeError if jpeg file contained
corrupt metadata. Closes http://dev.plone.org/ticket/12753.
[patch by joka, applied by kleist]

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* Fix test failure.
[davisagli]

* Fix bug in producing tag for a scale on an item with a unicode title
[tomster]

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* Make the ``download`` view respect custom read permissions for the field
being downloaded, rather than only checking the view permission for the
object as a whole.
[davisagli]

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* Fix bug in producing tag for a scale on an item whose title has non-ASCII
characters.
[davisagli]

* Make sure image scales of allowed attributes can be accessed on disallowed
containers.
[davisagli]

* Add unit tests for safe_filename, since not exercised within this module.
(should be moved to plone.formwidget.namedfile?)
[lentinj]