Added 3 new options to OrmLite.Poco.tt

Added 3 new options, to make OrmLite.Poco.tt output the classes I wanted:
- MakeSingular, default true. if true: Changes the classname to singular if tablename is not singular
- UseIdAsPk, default true. if true: Changes the primary key property name to Id
- GenerateConstructor, default false. if true: Generates the default empty constructor