Add simple Tensor class

src/backends/tensor.cpp

@@ -0,0 +1,11 @@
+#include "backend/tensor.hpp"
+
+using namespace CUDANet::Backend;
+
+Tensor::Tensor(Shape shape, DType dtype, IBackend* backend)
+    : shape(shape), dtype(dtype), backend(backend), devicePtr(nullptr), hostPtr(nullptr) {}
+
+Tensor::~Tensor() {
+    deallocate();
+}
+