Plone.app.caching

Bug fixes:

- Fixed title and description of max age in strong caching rule for resources.
They wrongly were the same as for shared max age.
Fixes `issue 1989 <https://github.com/plone/Products.CMFPlone/issues/1989>`_.
[maurits]

Bug fixes:

- Fix: Do not break Plone if there is no Archetypes available.
[jensens]

Bug fixes:

- Remove dependency on unittest2; fix tests assertions.
[hvelarde]

- Fixed tests when using ZODB 4.
[davisagli]

Bug fixes:

- Update code to follow Plone styleguide.
[gforcada]

Bug fixes:

- Code-Style: isort, utf8-headers, zca-decorators, manual cleanup.
[jensens]

Bug fixes:

- Enable unload protection by using pattern class ``pat-formunloadalert`` instead ``enableUnloadProtection``.
[thet]