backport stable branch and some vreg cleanups:
* move initialization_completed from cwvreg to base VRegistry class
allowing simplification of CWVregistry
* cleanup initialization process: __registered__ is now called after
initialization completed, by the relevant registry.
* fix/remove deprecated tests
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)