Add the ability to add automatic fields.

When selecting specific fields (such as computed fields) it is often
really helpful to also select all the fields in the model. Instead of
having to type out all the columns in the schema, the autoFields()
method can be used to tell an ORM\Query to also include the automatic
fields. This new method also works in contain() builders.

Refs #4360
Clean up code a bit.

Remove bonus ternary and array modification.
Fix tests for Database quoting situation.
Fix typo and failing test.
model -> table
Merge pull request #4381 from cakephp/orm-select-additional-fields

3.0 - ORM select additional fields