Addfkey

Currently, all databases for test are based on raw-ddl-creator. This module is not complete and a lot of functionality is missed. Right now, SQLite provider code can't generate FKEYS for CREATE_TABLE operation. This patch removes this limitation. The problem here, is that FK parameter for provider should be set to TRUE. Also, sqlite by itself should support FKEYS. It is true for recent version. I will try to port some test for new GdaDdlCreator module for testing DB generation. If this MR is very radical we may mark it as WIP.