Slc-outdated

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- Nothing changed yet.

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- Update import to fix a deprecation warning (fixes 4)
[ale-rt]

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- Support Plone 5.2 and Python3

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- Add p.a.testing setup and basic tests if the product is properly installed.
[jcbrand]
- Added missing autoinclude [thomasw]

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- Add utility method to directly check if an object is outdated, instead of
using the catalog. [jcbrand]

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- Toggle outdated now makes a general call to reindexObject (before, only
one index was re-indexed) so that the object's modification date gets set
[thomasw]
- An event now gets sent when the outdated status is changed; can be used for
custom handling of outdated content, e.g. regarding link checking [thomasw]
- Restructuring, removed all functional code from __init__.py [thomasw]