Update definition of an empty model.
Update tests for incorrect containable behaviour if a model only finds 1 field.
Merge pull request #2204 from thatcode/master

Models fetched by Containable find depend on number of fields in intermediate Model
Fix file always being set to 'schema.php'

When the name parameter is set and no custom file value is provided,
the name should be used to generate the file name. empty() cannot be
used because the file parameter has a default value of 'schema.php'.

Fixes #2202