Collective.messagesviewlet

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- Bypass allowed content types contraint when (post)install messagesConfig container
[boulch]

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- Added parameter `caching=True` to `utils.get_messages_to_show`, if `True`,
the method result is cached in the request for given `context`.
[gbastien]

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- Added PseudoMessage class that be be used in viewlet template.
[sgeulette]

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- Define version to `2000` in `metadata.xml` of plone4 profile or upgrade step
to 2000 is always displayed.
[gbastien]

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- Evaluate TAL condition using behavior `evaluate` method instead calling
directly submethod `utils.evaluateExpressionFor` so behavior method
`complete_extra_expr_ctx` is called.
[gbastien]
- Call JS on portal_url so it can be cached by the browser.
[gbastien]
- Tests on Plone5 and Plone4.
[bsuttor]
- Manage profiles differently
[sgeulette]
- Moved `MessagesViewlet.getAllMessages` code to `utils.get_messages_to_show`
so it is easily callable from outside.
[gbastien]
- Be defensive while managing TZ of message dates : do not set it if already
set, it fails, moreover, indexing a metadata from a date attribute that had
no TZ to one having TZ fails so undindex/reindex the entire message.
[gbastien]

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- Corrected import step dependencies to avoid unresolved warning. Save really changes !
[sgeulette]