This changeset defines on the field the (somehow) abstract SQL type a field
should use letting the duty of specifying the real SQL type the database
supports and the conversion to/from the python types to the backend.
issue6351
review33951002
* Use python-sql
* Add convert_domain method on Fields
* Add sql_format and sql_type methods on Fields
* Allow to return a full domain for Function.searcher
* Replace static backend by dynamic get method
* Replace order_field by order_<field name> method
review1001002
Cédric Krier