Refactored Interpolator to be an abstract interface class

CInterpolator is now an IInterpolator interface. Sublcass in order
to implement different types of interpolation.

refs #169

tests/blackcore/testinterpolator.cpp

@@ -14,8 +14,7 @@ namespace BlackCoreTest
  */
 void CTestInterpolator::interpolatorBasics()
 {
-    CInterpolator c;
-    QVERIFY2(!c.isValid(), "Default interpolator should not be valid");
+
 }
 
 } // namespace