close #472361: omit password and bytes attributes in allowed mass-mailing keys
by fixing default implementation for allowed_massmail_keys() in the
Emailable pluggable mixin (cw.common.mixins).
Added test (in entities.test though), also fix CWUserTC classes conflicts in the test module.
This directory contains extra libraries which are needed
to make cubicweb work.
The mx.DateTime python implementation is directly taken from
the mx.DateTime distribution. The only modification is the
strptime function which has been mocked using the standard
``datetime`` module. (as provided by the python2.5's stdlib)