BaseKernel.eval(..) should not declare a checked exception

[andrus]

BaseKernel.eval(..) should not declare a checked exception. It should throw some kind of RuntimeException instead. This will allow the extension classes to cut down the exception handling boilerplate:

public class DFLibJupyterExtension implements Extension {
   ... 
    @Override
    public void install(BaseKernel kernel) {
        try {
            kernel.eval(...);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}