Adding more Mat4x4 functionality

src/J3ML/LinearAlgebra/Matrix4x4.cpp

@@ -167,5 +167,9 @@ namespace LinearAlgebra {
         float p30 = 0;       float p31 = 0;       float p32 = 0.f;         float p33 = 1.f;
     }
 
+    float Matrix4x4::At(int x, int y) const {
+        return elems[x][y];
+    }
+
 
 }