Use template for endgame scaling functions

Also integrate scaling and evaluation in a
single base class.

Nice use of templates here :-)

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/material.h

@@ -63,8 +63,8 @@ private:
   int16_t mgValue;
   int16_t egValue;
   uint8_t factor[2];
-  EndgameEvaluationFunction* evaluationFunction;
-  ScalingFunction* scalingFunction[2];
+  EndgameEvaluationFunctionBase* evaluationFunction;
+  EndgameScalingFunctionBase* scalingFunction[2];
   uint8_t spaceWeight;
 };