A squashed merge is required as the conversion of the apiculture branch from
bzr to git was not correctly done. The git history contains irrelevant blobs
and commits. This branch brings a lot of changes and fixes, too many to list
exhaustively.

- New orm api, objects are now used instead of ids
- Environements to encapsulates cr uid context while maintaining backward compatibility
- Field compute attribute is a new object oriented way to define function fields
- Shared browse record cache
- New onchange protocol
- Optional copy flag on fields
- Documentation update
- Dead code cleanup
- Lots of fixes