unification of meta-attributes handling:
* remove has_format, has_text_encoding, format, text_encoding methods on Entity
* remove rich_text_fields method on EntitySchema
* use instead has_metadata / meta_attribute on EntitySchema (from yams)
and attribute_metadata on Entity
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)