DataSourceConstraint class hierarchy is too rigid

[efronbs]

Some downstream customers have had issues extending and using DataSourceConstraint and its subclasses. It should be made more extendable and flexible.

An interface has been extracted from the DataSourceConstraint class. The original DataSourceConstraint implementation has been renamed to BaseDataSourceConstraint. The rest of the class hierarchy has been maintained.

To absorb these changes switch all instances of explicitly creating a DataSourceConstraint to creating a BaseDataSourceConstraint. No other changes should be required.

A new method has been added to the interface which allows filtering a DataSourceConstraint's Dimenisions using a predicate. This is the Dimension side of the functionality already provided by withMetricIntersection.