Plone.app.testing

------------------

Bug fixes:

- Do not use install Products.PasswordResetTool in the PloneFixture if it isn't available.
[thet]

------------------

New features:

- Use get_installer instead of portal_quickinstaller when available, for
Plone 5.1 and higher. [maurits]

- In PloneSandboxLayer make profile upgrade versions persistent. This
way installed profile versions get reset in teardown. [maurits]

------------------

Bug fixes:

- Load Products.CMFFormController in tests. It is still used by core
Plone, also without Archetypes. This makes the CMFFormController
tests pass. [maurits]

------------------

Fixes:

- Do not use install Products.SecureMailHost in the PloneFixture if it isn't available
[vangheem]

------------------

Fixes:

- Replace deprecated ``zope.site.hooks`` import with ``zope.component.hooks``.
[thet]

------------------

New:

- Add a MOCK_MAILHOST_FIXTURE fixture that integration and functional tests layers can depend on.
This allows to easily check how mails are sent from Plone.
[gforcada]

Fixes:

- Fix ``layers.rst`` doctest to be compatible with older and newer zope.testrunner layer ordering.
[thet]

- Depend on ``zope.testrunner`` and fix deprecated usage of ``zope.testing.testrunner``.
[thet]

- Cleanup code, flake8, sort imports, etc.
[gforcada]

- Fix RAM cache error with bbb.PloneTestCase.
[ebrehault]