added CustomIndex capability only to Tensor and not yet to TensorBase.

using Sfinae and is_base_of to select correct template which converts to array<Index,NumIndices>


 user: Gabriel Nützi <gnuetzi@gmx.ch>
 branch 'default'
 added unsupported/Eigen/CXX11/src/Tensor/TensorMetaMacros.h
 added unsupported/test/cxx11_tensor_customIndex.cpp
 changed unsupported/Eigen/CXX11/Tensor
 changed unsupported/Eigen/CXX11/src/Tensor/Tensor.h
 changed unsupported/Eigen/CXX11/src/Tensor/TensorMeta.h
 changed unsupported/test/CMakeLists.txt

unsupported/Eigen/CXX11/src/Tensor/TensorMetaMacros.h

@@ -0,0 +1,33 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2015 Benoit Steiner <benoit.steiner.goog@gmail.com>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef EIGEN_CXX11_TENSOR_TENSOR_META_MACROS_H
+#define EIGEN_CXX11_TENSOR_TENSOR_META_MACROS_H
+
+
+/** use this macro in sfinae selection in templated functions
+ *
+ *   template<typename T,
+ *            typename std::enable_if< isBanana<T>::value , int >::type = 0
+ *   >
+ *   void foo(){}
+ *
+ *   becomes =>
+ *
+ *   template<typename TopoType,
+ *           SFINAE_ENABLE_IF( isBanana<T>::value )
+ *   >
+ *   void foo(){}
+ */
+
+#define EIGEN_SFINAE_ENABLE_IF( __condition__ ) \
+    typename internal::enable_if< ( __condition__ ) , int >::type = 0
+
+
+#endif