support for datatype in newer sync schemas

In Model converter, also validate messages in message_to_odoo.

Model converter argument changed, __type__ is now the last argument and is optional. It is expected not to be used anymore. Added possible_datatypes property and odoo_datatype on Converter. Defaults to empty set and None. On Model, it can be set.

Replace generic exceptions.

merged

mentioned in merge request redner!82 (merged)