PostgreSQL - Select<T> does not handle WITH query.

Falling test for http://stackoverflow.com/questions/22830117/servicestack-ormlite-select-throws-npgsql-syntax-error-when-using-with-cte

Select<T> thinks the sql string is a WHERE clause and generates the following invalid SQL.

```
DEBUG: SELECT "Id", "Name", "LongId", "Guid", "Bool", "DateTime", "Double" FROM "ModelWithFieldsOfDifferentTypes" WHERE 
					WITH max_id AS (
						SELECT 3 AS three)
					SELECT *
					FROM ModelWithFieldsOfDifferentTypes
					WHERE id <= (SELECT three FROM max_id)
Npgsql.NpgsqlException : ERROR: 42601: syntax error at or near "WITH max_id"