add subscript operator for CollisionList

libraries/shared/src/CollisionInfo.cpp

@@ -48,3 +48,6 @@ void CollisionList::clear() {
     _size = 0;
 }
 
+const CollisionInfo* CollisionList::operator[](int index) const {
+    return (index > -1 && index < _size) ? &(_collisions[index]) : NULL;
+}

libraries/shared/src/CollisionInfo.h

@@ -95,6 +95,8 @@ public:
     /// Clear valid collisions.
     void clear();
 
+    const CollisionInfo* operator[](int index) const;
+
 private:
     int _maxSize;   // the container cannot get larger than this
     int _size;      // the current number of valid collisions in the list