PLIP 7822: ZODB Blob support for file & image content
=====================================================

This PLIP is ready for review.

Trac ticket: http://dev.plone.org/plone/ticket/7822


Summary of changes
------------------

- Added `plone.app.blob` as a dependency to `Plone`.

- Fixed test setup for `Plone` to include a blob storage.

- Fixed `ATContentTypes` tests to reflect the changes due to the different
  base class.


To do
-----

- Provide benchmarks for file, image content as well as image scales at
  various sizes to make sure there is no performance regression using blobs.

- Push fixes for `Zope` which currently live in monkey-patches upstream for
  inclusion into 2.12.

- Push patch for `Archetypes` from `plone.app.imaging` upstream.

- Resolve test setup problem with ZODB 3.9.

- Fix remaining test failures regarding image support in `Plone` and
  `ATContentTypes` tests.  The number of failures matches those in Plone 3.3,
  so the upgrade to Plone 4.0 doesn't introduce new issues (also see
  http://blobot.zitc.de/ for the current status).

- Fix issue regarding image transformations (see ticket #8506).

- Fix issues regarding versioning with `CMFEditions`.

- Address remaining issues (see issues for target release 1.0 at
  http://plone.org/products/plone.app.blob/issues)


Needed documentation changes
----------------------------

Necessary changes to buildouts (esp with ZEO), migration of existing content
as well as a backup strategy need to be documented.  Most of this is already
addressed at the product pages at PyPI and plone.org, but some things need
updating.

Also, developer documentation of how to use blobs in custom content types
needs to be added.  This should also describe the changes and the new
locations of the used base classes.


Backwards compatibility
-----------------------

The packages aim to provide fully backward-compatible versions of the existing
content type implementations.  A buildbot is provided to ensure this for all
minor versions in the 3.x series as well as for Plone 4.0.


Credits
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Andreas Zeidler