Type-safe DataSet Identifier Interface

[nikolausmoll]

Remove general "Object" return type in IScope, rename class as well. DslIdentifier could be part of type information T

Is:

     public interface IScope
     {

       Object getDataSet();

       String getDslIdentifier();

     }

Should (or similar):

     public interface IScope<T>
     {

       T getDataSet();

     }

Problem:
Both the new Table Builder and the "classic" DataSet must represent the same Scope type (DSL identifer / T).
The class (DSL identifier) of the DataSet is used to distinguish different DSL types. But as the base DataSet class is abstract, the dataset's getClass() method will not return the type of the abstract DataSet class.