Add forgotten doc
On the non required onetoone relations, we only validate the required children if at least one value is posted.
* Delete the old value from the DB for the onetoone field
* Improve the tests
If no value posted for onetoone field, we return None to delete the value from the DB
Test the non required onetoone field
Merge pull request #12 from LeResKP/feature/onetoone_relation

Improve the onetoone relation
2.0.5
Some progress on modernizing tests.
Failures done.  Errors left.
Last errors dealt with.  Thank god.
2.0.6
Merge branch 'release/2.0.6' into develop
Metadata fixups, tw2.core#90
Add missing require for the tests
Fix tw.Param: the attribute is always defined and required.
s/setup/setUp/g
Fix tests
For genshi we should not call __call__ many times on the same the widget
Some refactoring
Display the onetoone field in a label when we view the data. In this way the HTML table is not too big according to the DB.