Global image counting

Is useful later for when we want to know our progress

DescriptorManager.h

@@ -39,6 +39,7 @@ private:
 	//TODO: automagically update this?
 
 	bool initialized = false;
+	int numImages;
 
 	map<string, bitset<64>> features[numDescriptors]; //array of maps that will hold the descriptors
 	map<string, bitset<64>> mutatedFeatures[numDescriptors][numMutations];