transform DateTime object into ODF acceptable format
  '2009/04/20' -> '2009-04-20'

* Append
  test cases which confirm fixing the bugs

* Refactoring
  - change method name into mixedCase, according to 
    the naming convention
  - using etree nsmap object instead of to define 
    the namespace-dictionary constant
  - the long test method devide into appropriate
    some methods



git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@26344 20353a03-c40f-0410-a6d1-a30d3c3de9de