Collective-monitor

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- Fix error if last_login is empty.
[bsuttor]

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- Return date in ISO format
[bsuttor]

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- Add a probe (dates) which return all probes date.
[bsuttor]

- Add last_login_time porbe.
[bsuttor]

- Add last_modified_plone_object_time probe.
[bsuttor]

- Add last_modified_zope_object_time probe.
[bsuttor]

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- Date probe are not more in stats probe (from Products.ZNagios).
[bsuttor]

- Add creation_date_plonesite probe
[bsuttor]

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- Return number of smtp errors found.
[bsuttor]

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- Add count_users probe
[bsuttor]

- Initial package
[bsuttor]