#15 introduce generated id by a model transformation

[Joerg Reichert]

currently the usage of a generic id attribute of type Long in each entity is spreaded over several templates and extensions (POJO definition, validator for Long and at some more places). A better way to introduce the id attribut is to define a model transformation. This model transformation realizable through oAW's xTend language would give every entity in the data model an additional attribut with name id and data type ELongObject.