Plone-app-caching

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- Remove DL's from portal message templates.
https://github.com/plone/Products.CMFPlone/issues/153
[khink]

- Fix ruleset registry test isolation so that is no longer order dependent.
[jone]

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- Fix tests that fail on the day before the switch to daylight saving time.
[pbauer]

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- Use the PLONE_APP_CONTENTTYPES_FIXTURE test layer for Plone 5 compatibility.
[timo]

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- Make it possible to set a maxage of zero in strong caching. This is
an edge case since this would ordinarily be handled by moderate caching.
[smcmahon]

- Add some testing for weak caching operations.
[smcmahon]

- Fix handling of anon-only flag for cases where maxage is not zero. It
was effectively ignored. Added operation test for strong caching.
[smcmahon]

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- Fix double purge of paths for items whose default view is the same as /view
[eleddy]

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- Register the plone.atobjectfields adapter not only when Products.Archetypes
but also plone.app.blob is installed.
[thet]