Master exceptions b sig

Using UserError, AccessError, MissingError, ValidationError instead of except_orm and except_osv.
Using _logger.info instead of _logger.warning to avoid polluating Sentry

Needs testcases for all former cases: one with a single argument e.g. `Warning('description')`, one with `except_orm` and 2 arguments, and one with `UserError` and a single argument