Enable CakePHP ORM to accept PostgreSQL and SQL Server schema.
Add tests for postgres + sqlserver schema.table names.

Both postgres and sqlserver databases frequently use multiple schemas.
As per #3924 and #3914 both sqlserver and postgres support
`schema.table` style table names allowing specific models to use tables
on schemas outside of the default schema.
Merge pull request #4340 from cakephp/schema-name

Schema name for postgres and sqlserver